The present invention concerns pyrrol-free analogues of porphyrins, their method of preparation and their use thereof especially in the fields of photonics, organic electronics including photovoltaics, optoelectronics and biology including photodynamic therapies.

TT-conjugated organic molecules (cyclic and/or linear) are widely used in the field of photonics, organic electronics including photovoltaics, optoelectronics and biology due to their geometrical and electronic structures which give them unique properties. The optic and electronic properties of those ττ-conjugated organic molecules are linked to a parameter named HOMO-LUMO gap (Eg) which corresponds to the energy difference between the Highest Occupied Molecular Orbital (HOMO) and the Lowest Unoccupied Molecular Orbital (LUMO). This gap should be as low as possible for the above-mentioned applications.

The molecules presenting a low Eg gap are often molecules of high dimensions. However, those molecules are weakly soluble which could be a huge limitation for the above mentioned applications. It is thus important to find new ττ-conjugated molecules that could present a low Eg gap and which could be soluble in organic medium and water.

Photodynamic therapy (PDT) is a form of phototherapy using nontoxic light-sensitive compounds that are exposed selectively to light, whereupon they becomes toxic to targeted malignant and other diseased cells, and thus can be used in the treatment of cancer for example. Most modern PDT applications involve three key components: a photosensitizer, a light source and oxygen. The wavelength of the light source needs to be appropriate for exciting the photosensitizer to produce reactive oxygen species. The combination of these three components leads to the chemical destruction of any tissues which have either selectively taken up the photosensitizer or have been locally exposed to light. This method has some disadvantages since only cancers accessible to light can be treated such as cancers near the surface of the skin (for example red light only has a penetration of about 1 cm in living tissues). In order to treat other cancers which require a higher penetration into the tissues, the photosensitizer used should absorb in the near infrared region (NIR region) as those radiations penetrate more deeply in the skin.

Regarding photovoltaic technology, about 50% of the solar energy is in the near infrared region. Thus one of the major limiting factors for organic solar cells is the gap between the spectral absorption of the active layer and the solar emitting spectrum. The organic devices actually use various molecules in order to absorb the major part of the solar energy (from visible to near infrared). The use of a unique organic molecule absorbing on a large scale would enable an improvement in yield and costs. Organic solar cells, are based on a blend or an electron donor and hole transporting material (such as polythiophene) mixed with an electron acceptor and electronic conductor material (generally fullerene derivatives). Most of the photovoltaic cells actually used are based on silicon. However, this material is expensive and difficult to recycle. Dye-photosensitized solar cells also called Gratzel (or Graetzel) cells have been developed based on sensitized inorganic/organic hybride semi-conductors instead of silicon. In Gratzel cell, upon photo absorption, the dye injects an electron in the conduction band of the semi-conductor. These cells especially implement less expensive material, simple and low cost production techniques. Modules obtained are semi-flexible and semi-transparent which also open larger fields of application. There is thus a need to develop dyes for this type of solar cells with improved photoconversion efficiency.

Among the ττ-conjugated molecules, porphyrins are probably the most important and adaptable macrocycles. The major research activity on porphyrins covers a broadest area ranging from chemistry, materials science, physics, biology, engineering and medicine. Porphyrins are highly conjugated heterocyclic macrocycles composed of four pyrrol subunits interconnected via one-atom bridges forming a 16-membered central ring. These porphyrins present 18 delocalized ττ-electrons. However, these porphyrins do not absorb in the NIR region.

Also known from Muranaka et al (JACS, 2012, 134, 190-193) are analogues of hemiporphyrazine which absorb in the NIR region. However, these compounds are not versatile since their modifications are very limited. Indeed, it should be very useful to modify the macrocyclic molecule in order to tune the Eg gap, the control the solubility, the geometry, etc...

As a consequence there is a need to provide new macrocyclic molecules with properties that can be easily tailored upon chemical modifications (i.e. high versatility), and that have small dimensions, low Eg gap and absorbance in the NIR region.

The objective of the present invention is to provide aromatic macrocycles of small dimensions, preferably high symmetry and which are stable over time in various media.

Another objective of the present invention is to provide such macrocycles easily accessible (i.e. easy chemical engineering which allows high versatility).

Another objective is also to provide such macrocycles which can absorb light in a large spectral range and more specifically in the NIR region.

Another objective of the present invention is also to provide macrocycles which can be used in solar cells, such as in organic solar cells and particularly as dye for dye-sensitized solar cells (Gratzel cells).

Other objectives should appear by reading the below description of the invention. All these objectives are met by the compounds according to the invention which comprise a central 16-membered ring bearing four nitrogen atoms and 18 ττ-electron and four 6-membered ring subunits.

The present invention relates to compound of formula (I):

(I)

in which : represents a single bond or a double bond provided that the central ring comprising 16 members (4 nitrogen atom and 12 carbon atoms) is an aromatic ring;

each R and R ² are identical or different and represent:

- a hydrogen atom;

- an aliphatic chain, linear or branched, comprising from 1 to 30 carbon atoms;

- a group of formula -(L ) _n -A-(R) _r ;

with the proviso that at least one of R and/or of R ² is different from H;

A represents a cycloalkyl, heterocycloalkyl, an aryl or heteroaryl group, monocyclic or polycyclic; or an aliphatic chain, linear or branched, comprising from 1 to 30 carbon atoms; r is an integer and represents from 0 to 5, for example 0, 1 or 2;

R, each identical or different represents:

- COR ³ ,

- OR ⁴ ,

- P0 ₃ H ₂ ,

- an alkyl chain, linear or branched comprising from 1 to 30 carbon atoms optionally substituted by at least one of (=0), OR ⁴ , COR ³ and/or P0 ₃ H ₂ ;

- an aryl or heteroaryl optionally mono or polysubstituted by COR ³ , OR ⁴ , P0 ₃ H ₂ , an alkyl chain, linear or branched comprising from 1 to 30 carbon atoms optionally substituted by at least one of (=0), OR ⁴ , COR ³ and/or P0 ₃ H ₂ ; R ³ represents hydrogen, OR ⁴ , a linear or branched alkyl comprising from 1 to 30 carbon atoms and optionally substituted by at least one group (=0) and/or OR ⁴ group;

R ⁴ represents H, a linear or branched alkyl comprising from 1 to 30 carbon atoms; n represents 0 or 1 ;

each L , identical or different, represents a linear or branched alkenyl or alkynyl comprising from 2 to 30 carbon atoms and comprising at least one double bond and/or at least one triple bond, preferably at least one of the double or triple bond is conjugated with the double bonds of the central ring and optionally with the double bond of A and optionally the double or triple bonds of L are conjugated with each other.

Preferably, in the compound of formula (I), A represents an aryl, an heteroaryl or an aliphatic chain, linear or branched, comprising from 1 to 30 carbon atoms, preferably A represents aryl, preferably phenyl, or an aliphatic chain, linear or branched, comprising from 1 to 30 carbon atoms.

Preferably, in the compound of formula (I), at least one of R and/or R ² is -(L ) _n -A-(R) _r and R, identical or different represents:

- COOH,

- OH, preferably when A is phenyl there are at least two OH groups in ortho position; - P0 ₃ H ₂ ,

- a C(0)CH ₂ C(0)Alk group, a C(0)CH(Alk)C(0)Alk group, a C(0)CH ₂ C(0)H group, a C(0)CH(Alk)C(0)H; wherein Alk is a linear or branched alkyl group comprising from 1 to 30 carbon atoms, preferably from 1 to 5 carbon atoms;

- an aryl substituted by a COOH or two OH groups in ortho position one relative to the other, a P0 ₃ H ₂ group, a C(0)CH ₂ C(0)Alk group, a C(0)CH(Alk)C(0)Alk group, a

C(0)CH ₂ C(0)H group, a C(0)CH(Alk)C(0)H; wherein Alk is a linear or branched alkyl group comprising from 1 to 30 carbon atoms, preferably from 1 to 5 carbon atoms.

Advantageously, the compounds of the present invention comprise in R and/or R ² : COOH groups, P0 ₃ H ₂ groups, C(0)CH ₂ C(0)Alk groups, C(0)CH(Alk)C(0)Alk groups, C(0)CH ₂ C(0)H groups, C(0)CH(Alk)C(0)H groups, two OH groups which are functions that enable to chelate a compound and especially a Ti0 ₂ compounds in solar cells.

Preferably, in the compound of formula (I) n is 0, and A is chosen among alkyl comprising from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, aryl comprising from 6 to 10 carbon atoms (mono or polycyclic) or heteroaryl comprising from 5 to 10 members (mono or polycyclic). Preferably, A is phenyl. In another embodiment of the present invention n is 1 and A is chosen among alkyl comprising from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, aryl comprising from 6 to 10 carbon atoms (mono or polycyclic) or heteroaryl comprising from 5 to 10 members (mono or polycyclic). Preferably, A is phenyl, and L represents a linear or branched alkenyl or alkynyl comprising from 2 to 30 carbon atoms and comprising at least one double bond and/or at least one triple bond, the double or triple bond being conjugated with the double bond of the central ring of formula (I), with the double bonds of A and with the other double bonds or triple bonds of L if L comprises more than four carbon atoms.

In a specific embodiment, the present invention relates to compound of formula (I):

represents a s ng e on or a ou e on prov e that the central ring comprising 16 members (4 nitrogen atom and 12 carbon atoms) is an aromatic ring;

each R and R ² are identical or different and represent:

- a hydrogen atom;

- an aliphatic chain, linear or branched, comprising from 1 to 30 carbon atoms;

- a group of formula -(L ) _n -A-COR ³ ; -(L ) _n -A-P0 ₃ H ₂ ; or -A-(R ⁵ ) _q

with the proviso that at least one of R and/or of R ² is different from H

A represents a cycloalkyl, heterocycloalkyl, aryl or heteroaryl group, monocyclic or polycyclic, each optionally mono- or poly-substituted for example by a linear or branched alkyl comprising from 1 to 30 carbon atoms and/or a group OR ⁴ ; or an aliphatic chain, linear or branched, comprising from 1 to 30 carbon atoms;

R ³ represents hydrogen, OR ⁴ , a linear or branched alkyl comprising from 1 to 30 carbon atoms and optionally substituted by at least one group (=0) and/or OR ⁴ ; R ⁴ represents H, a linear or branched alkyl comprising from 1 to 30 carbon atoms; q is an integer and represents from 1 to 5, for example 1 or 2;

R ⁵ , identical or different represents:

- OR ⁴ ;

- an alkyl chain, linear or branched comprising from 1 to 30 carbon atoms optionally substituted by at least one of (=0), OR ⁴ , P0 ₃ H ₂ , and/or COR ³ ;

- aryl or heteroaryl optionally mono or polysubstituted by:

o a linear or branched alkyl comprising from 1 to 30 carbon atoms optionally substituted by at least one (=0), OR ⁴ , P0 ₃ H ₂ , and/or COR ³ ; o a group OR ⁴ ;

o a group P0 ₃ H ₂ ; and/or

o a group COR ³ ;

n represents 0 or 1 ;

L is as defined above.

In one embodiment of the present invention, A represents an aryl, an heteroaryl or an aliphatic chain, linear or branched, comprising from 1 to 30 carbon atoms, preferably A represents aryl, preferably phenyl, or an aliphatic chain, linear or branched, comprising from 1 to 30 carbon atoms.

Preferably, in the compounds of the invention, each R and R ² are identical or different and represent:

- a hydrogen atom;

- an aliphatic chain, linear or branched, comprising from 1 to 30 carbon atoms;

- a group of formula -(L ) _n -A-COR ³ ; -(L ) _n -A-P0 ₃ H ₂ ; or -A-(R ⁵ ) _q

with the proviso that at least one of R and/or of R ² is different from H and that at least one of R and/or R ² is -(L ) _n -A-COR ³ ; -(L ) _n -A-P0 ₃ H ₂ ; or -A-(R ⁵ ) _q ;

A represents a aryl or heteroaryl group, monocyclic or polycyclic, preferably aryl, for example phenyl, each optionally mono- or poly-substituted for example by a linear or branched alkyl comprising from 1 to 30 carbon atoms and/or a group OR ⁴ ;

R ³ represents hydrogen, OR ⁴ , a linear or branched alkyl comprising from 1 to 30 carbon atoms and optionally substituted by at least one group (=0) and/or OR ⁴ ;

R ⁴ represents H, a linear or branched alkyl comprising from 1 to 30 carbon atoms; q is an integer and represents from 1 to 5, for example 1 or 2;

R ⁵ , identical or different represents:

- OR ⁴ ; - linear or branched alkyl comprising from 1 to 30 carbon atoms optionally substituted by at least one (=0), OR ⁴ , P0 ₃ H ₂ , and/or COR ³ ;

- aryl or heteroaryl optionally mono or polysubstituted by:

o a linear or branched alkyl comprising from 1 to 30 carbon atoms optionally substituted by at least one (=0), OR ⁴ , P0 ₃ H ₂ and/or COR ³ ; o a group OR ⁴ ;

o a group P0 ₃ H ₂ ; and/or

o a group COR ³ ;

n represents 0 or 1 ;

L is as defined above.

Preferably, in the compounds of the invention, each R and R ² are identical or different and represent:

- a hydrogen atom;

- an aliphatic chain, linear or branched, comprising from 1 to 30 carbon atoms;

- a group of formula -(L ) _n -A-COR ³ ; -(L ) _n -A-P0 ₃ H ₂ ; or -A-(R ⁵ ) _q;

with the proviso that at least one of R and/or of R ² is different from H and that at least one of R and/or R ² is a group of formula -(L ) _n -A-COR ³ ; -(L ) _n -A-P0 ₃ H ₂ ; or -A-(R ⁵ ) _q ;

A represents an aliphatic chain, linear or branched, comprising from 1 to 30 carbon atoms;

R ³ represents hydrogen, OR ⁴ , a linear or branched alkyl comprising from 1 to 30 carbon atoms and optionally substituted by at least one group (=0) and/or OR ⁴ ;

R ⁴ represents H, a linear or branched alkyl comprising from 1 to 30 carbon atoms; R ⁵ represents aryl or heteroaryl optionally substituted by at least a linear or branched alkyl comprising from 1 to 30 carbon atoms, a group OR ⁴ and/or a group COR ³ ;

q is an integer and represents from 1 to 5, for example 1 or 2;

R ⁵ , identical or different represents:

- OR ⁴ ;

- aryl or heteroaryl optionally mono or polysubstituted by:

o a linear or branched alkyl comprising from 1 to 30 carbon atoms optionally substituted by at least one group (=0), and/or OR ⁴ group, a group P0 ₃ H ₂ , a group COR ³ ;

o a group OR ⁴ ;

o a group P0 ₃ H ₂ ; and/or

o a group COR ³ ;

n represents 0 or 1 ;

L is as defined above. Preferably, in the compounds of the invention, each R and R ² are identical or different and represent:

- a hydrogen atom;

- an aliphatic chain, linear or branched, comprising from 1 to 30 carbon atoms

- a group of formula -(L ) _n -A-COOR ⁴ ; -(L ) _n -A-CO-alk-CO-alk; -(L ) _n -A-CO-alk-COH;- (L ) _n -A-P0 ₃ H ₂ ; -A-aryl, the aryl being substituted by two OH group in ortho position one relative to the other and/or one CO group and one OH group in ortho position one relative to the other;

with the proviso that at least one of R and/or of R ² is different from H and at least one of R and/or of R ² is selected among a group of formula -(L ) _n -A-COOR ⁴ ; -(L ) _n -A-CO-alk- CO-alk; -(L ) _n -A-CO-alk-COH;-(L ) _n -A-P0 ₃ H ₂ ; -A-aryl, the aryl being substituted by two OH group in ortho position one relative to the other and/or one CO group and one OH group in ortho position one relative to the other ;

n and L being as defined above;

R ⁴ represents H, a linear or branched alkyl comprising from 1 to 30 carbon atoms; Alk represents a linear or branched alkyl comprising from 1 to 30 carbon atoms, preferably alk is CH ₂ ;

A represents a cycloalkyl, heterocycloalkyl, aryl or heteroaryl group, monocyclic or polycyclic, preferably aryl, for example phenyl, each optionally mono- or poly-substituted for example by a linear or branched alkyl comprising from 1 to 30 carbon atoms and/or a group OR ⁴ ; or an aliphatic chain, linear or branched, comprising from 1 to 30 carbon atoms.

Preferably, in the compounds of the invention, each R and R ² are identical or different and represent:

- a hydrogen atom;

- an aliphatic chain, linear or branched, comprising from 1 to 30 carbon atoms

-a group of formula -(L ) _n -A-COOR ⁴ ; -(L ) _n -A-C(0)CH ₂ C(0)Alk, -(L ) _n -A- C(0)CH(Alk)C(0)Alk, -(L ) _n -A-C(0)CH ₂ C(0)H, -(L ) _n -A-C(0)CH(Alk)C(0)H ; -(L ) _n -A-P0 ₃ H ₂ ; -A-aryl, the aryl being substituted by two OH groups in ortho position one relative to the other and/or one CO group and one OH group in ortho position one relative to the other; with the proviso that at least one of R and/or of R ² is different from H and at least one of R and/or of R ² is selected among a group of formula -(L ) _n -A-COOR ⁴ ; -(L ) _n -A- C(0)CH ₂ C(0)Alk, -(L ) _n -A-C(0)CH(Alk)C(0)Alk, -(L ) _n -A-C(0)CH ₂ C(0)H, -(L ) _n -A- C(0)CH(Alk)C(0)H ; -(L ) _n -A-P0 ₃ H ₂ ; -A-aryl, the aryl being substituted by two OH group in ortho position one relative to the other and/or one CO group and one OH group in ortho position one relative to the other ; n and L being as defined above;

R ⁴ represents H, a linear or branched alkyl comprising from 1 to 30 carbon atoms; Alk represents a linear or branched alkyl comprising from 1 to 30 carbon atoms;

A represents an aryl or heteroaryl group, monocyclic or polycyclic, preferably aryl, for example phenyl, each optionally mono- or poly-substituted for example by a linear or branched alkyl comprising from 1 to 30 carbon atoms and/or a group OR ⁴ .

Preferably, in the compounds of the invention, each R and R ² are identical or different and represent:

- a hydrogen atom;

- an aliphatic chain, linear or branched, comprising from 1 to 30 carbon atoms;

- a group of formula -(L ) _n -A-COOR ⁴ ; -(L ) _n -A-CO-alk-CO-alk; -(L ) _n -A- C(0)CH ₂ C(0)Alk, -(L ) _n -A-C(0)CH(Alk)C(0)Alk, -(L ) _n -A-C(0)CH ₂ C(0)H, -(L ) _n -A- C(0)CH(Alk)C(0)H-(L ) _n -A-P0 ₃ H ₂ ; -A-aryl, the aryl being substituted two OH group in ortho position one relative to the other and/or one CO group and one OH group in ortho position one relative to the other;

with the proviso that at least one of R and/or of R ² is different from H and at least one of R and/or of R ² is selected among a group of formula -(L ) _n -A-COOR ⁴ ; -(L ) _n -A-CO-alk- CO-alk; -(L ) _n -A-C(0)CH ₂ C(0)Alk , -(L ) _n -A-C(0)CH(Alk)C(0)Alk, -(L ) _n -A-C(0)CH ₂ C(0)H, - (L ) _n -A-C(0)CH(Alk)C(0)H-(L ) _n -A-P0 ₃ H ₂ ; -A-aryl, the aryl being substituted two OH group in ortho position one relative to the other and/or one CO group and one OH group in ortho position one relative to the other;

n and L being as defined above;

R ⁴ represents H, a linear or branched alkyl comprising from 1 to 30 carbon atoms; Alk represents a linear or branched alkyl comprising from 1 to 30 carbon atoms;

A represents an aliphatic chain, linear or branched, comprising from 1 to 30 carbon atoms.

Preferably, in the compounds of the invention, each R and R ² are identical or different and represent:

- a hydrogen atom;

- an aliphatic chain, linear or branched, comprising from 1 to 30 carbon atoms;

- a group of formula -(L ) _n -A-COOH; -(L ) _n -A-acetylacetonate; -(L ) _n -A-P0 ₃ H ₂ ; -A- catechol;

with the proviso that at least one of R and/or of R ² is different from H and at least one of R and/or of R ² is selected among a group of formula -(L ) _n -A-COOH; -(L ) _n -A- acetylacetonate; -(L ) _n -A-P0 ₃ H ₂ ; -A-catechol; n and L being as defined above;

A represents a cycloalkyl, heterocycloalkyl, aryl or heteroaryl group, monocyclic or polycyclic, preferably aryl, for example phenyl, each optionally mono- or poly-substituted for example by a linear or branched alkyl comprising from 1 to 30 carbon atoms and/or a group OR ⁴ ; or an aliphatic chain, linear or branched, comprising from 1 to 30 carbon atoms.

Preferably, in the compounds of the invention, each R and R ² are identical or different and represent:

- a hydrogen atom;

- an aliphatic chain, linear or branched, comprising from 1 to 30 carbon atoms;

- a group of formula -(L ) _n -A-COOH; -(L ) _n -A-acetylacetonate; -(L ) _n -A-P0 ₃ H ₂ ; -A- catechol;

with the proviso that at least one of R and/or of R ² is different from H and at least one of R and/or of R ² is selected among a group of formula -(L ) _n -A-COOH; -(L ) _n -A- acetylacetonate; -(L ) _n -A-P0 ₃ H ₂ ; -A-catechol;

n and L being as defined above;

A represents a aryl or heteroaryl group, preferably aryl, monocyclic or polycyclic, preferably aryl, for example phenyl, each optionally mono- or poly-substituted for example by a linear or branched alkyl comprising from 1 to 30 carbon atoms and/or a group OR ⁴ .

Preferably, in the compounds of the invention, each R and R ² are identical or different and represent:

- a hydrogen atom;

- an aliphatic chain, linear or branched, comprising from 1 to 30 carbon atoms;

- a group of formula -(L ) _n -A-COOH; -(L ) _n -A-acetylacetonate; -(L ) _n -A-P0 ₃ H ₂ ; -A- catechol;

with the proviso that at least one of R and/or of R ² is different from H and at least one of R and/or of R ² is selected among a group of formula -(L ) _n -A-COOH; -(L ) _n -A- acetylacetonate; -(L ) _n -A-P0 ₃ H ₂ ; -A-catechol;

n and L being as defined above;

A represents an aliphatic chain, linear or branched, comprising from 1 to 30 carbon atoms.

In one embodiment in the compounds of the present invention n is 0, A is chosen among alkyl comprising from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, aryl comprising from 6 to 10 carbon atoms (mono or polycyclic) or heteroaryl comprising from 5 to 10 members (mono or polycyclic) wherein the aryl or heteroaryl is optionally mono- or poly- substituted for example by a linear or branched alkyl comprising from 1 to 30 carbon atoms and/or a group OR ⁴ . Preferably, A is phenyl optionally mono- or poly-substituted for example by a linear or branched alkyl comprising from 1 to 30 carbon atoms and/or a group OR ⁴ . In another embodiment of the present invention n is 1 and A is chosen among alkyl comprising from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, aryl comprising from 6 to 10 carbon atoms (mono or polycyclic) or heteroaryl comprising from 5 to 10 members (mono or polycyclic) wherein the aryl or heteroaryl is optionally mono- or poly- substituted for example by a linear or branched alkyl comprising from 1 to 30 carbon atoms and/or a group OR ⁴ . Preferably, A is phenyl optionally mono- or poly-substituted for example by a linear or branched alkyl comprising from 1 to 30 carbon atoms and/or a group OR ⁴ , and L represents a linear or branched alkenyl comprising from 2 to 30 carbon atoms and comprising at least one double bond and/or at least one triple bond, the double or triple bond being conjugated with the double bond of the central ring of formula (I), with the double bonds of A and with the other double bonds or triple bonds of L if L comprises more than four carbon atoms.

Preferably the compounds of the invention, each R1 and R2 are identical or different and represent:

- a hydrogen atom;

- an aliphatic chain, linear or branched, comprising from 1 to 30 carbon atoms;

- a group of formula - (L ) _n -A-COOH wherein A represents an aliphatic chain, linear or branched, comprising from 1 to 30 carbon atoms, for example from 1 to 5 carbon atoms, an aryl or heteroaryl group, monocyclic or polycyclic, the monocycle or polycycle being optionally mono- or polysubstituted by for example a linear or branched alkyl comprising from 1 to 30 carbon atoms and/or a group OR ⁴ ;

- with the proviso that at least one of R and/or R ² is different from H and at least one of R and/or of R ² is selected among a group of formula -(L ) _n -A-COOH. In another embodiment of the present invention each R and R ² are identical or different and represent:

- a hydrogen atom;

- an aliphatic chain, linear or branched, comprising from 1 to 30 carbon atoms;

- a group of formula— (L ) _n -A -COOH wherein A ¹ represents a, aryl or heteroaryl group, monocyclic or polycyclic, the monocycle or polycycle being optionally mono- or polysubstituted by for example by a linear or branched alkyl comprising from 1 to 30 carbon atoms and/or a group OR ⁴ ; with the proviso that at least one of R and/or R ² is different from H and at least one of R and/or of R ² is selected among a group of formula -(L ) _n -A -COOH.

Preferably, in this embodiment A ¹ is chosen among aryl comprising from 6 to 10 carbon atoms or heteroaryl comprising from 5 to 10 members and when n is 1 , L represents a linear or branched alkyl comprising from 2 to 30 carbon atoms and comprising at least one double bond and/or at least one triple bond, the double or triple bond being conjugated with the double bond of the central ring of formula (I) and with the double bonds of A and with the other double bonds or triple bonds of L if L comprises more than four carbon atoms. Preferably, A ¹ is phenyl optionally substituted and when n is 1 , L represents a linear or branched alkyl comprising from 2 to 30 carbon atoms and comprising at least one double bond and/or at least one triple bond, the double or triple bond being conjugated with the double bond of the central ring of formula (I) and with the double bonds of A and with the other double bonds or triple bonds of L if L comprises more than four carbon atoms.

Preferably, in this embodiment n is 0.

In another embodiment of the present invention each R and R ² are identical or different and represent:

- a hydrogen atom;

- an aliphatic chain, linear or branched, comprising from 1 to 30 carbon atoms;

- a group of formula alkyl-COOH, wherein the alkyl is linear or branched and comprised from 1 to 30 carbon atoms, preferably from 1 to 10 carbon atoms, for example from 1 to 5 carbon atoms,

with the proviso that at least one of R and/or R ² is different from H and at least one of R and/or of R ² is selected among a group of formula alkyl-COOH.

Preferably, in the compounds according to the invention R ² represents H and R is as defined above in the different embodiments presented, with the proviso that at least one of R is different from H and at least one of the R is selected among a group of formula -(L ) _n - A-COR ³ ; -(L ) _n -A-P0 ₃ H ₂ ; or -A-(R ⁵ ) _q .

According to the present invention:

- aryl is an aromatic mono- or polycycle comprising from 6 to 10 carbon atoms, preferably phenyl;

- cycloalkyl is a mono- or polycycle comprising from 5 to 10 carbon atoms;

- heteroaryl is an aromatic mono- or polycycle comprising from 5 to 10 members including at least one heteroatom for example chosen among N, O, S; - heterocycloalkyl is a mono- or polycycle comprising from 5 to 10 members including at least one heteroatom for example chosen among N, O, S.

It should be understood that compounds of formula (I) according to the invention are bis-zwitterionic compounds in which two positive charges and two negative charges are delocalized.

It should also be understood that represents either a single bond or a double bond, which are delocalized in the cycle. Formula (I) comprises especially the following formul

Those formulae show the delocalisation of the positive charge but it should be understood that the negative charge is also delocalisable in the central ring.

As mentioned above, the invention also relates to compounds of formula (I) in their ionic forms. Those compounds in ionic forms can be obtained by reacting the bis-zwitterionic compounds of formula (I) with at least one mole of an acid. The acid being preferably chosen among CF ₃ COOH or HX, X being an anion (halogen atom, BF ₄ ^~ , PF ₆ ^" , CI0 ₄ ^" etc .). Those compounds in ionic form can be as follows:

(la) or (lb)

wherein Z represents an anion, for example X, BF ₄ , PF ₆ , CI0 ₄ or CF ₃ COO.

Preferably, the compounds in ionic form are of formula (lb).

The compounds in ionic form can also be obtained by reacting the bis-zwitterionic compounds of formula (I) with at least one mole of a base. The base is preferably chosen among strong base, for example base chosen among NEt ₃ , NaOtBu, BuLi, NaOH.

Those compounds in ionic form can be as follows:

or

wherein W represents Na, NHEt ₃ , Li.

Preferably, the compounds in ionic form are of formula (lc') et (Id').

As mentioned above, the invention also relates to compounds of formula (I) in the form of chelates since Density Functional Theory (DFT) calculation (as shown in the examples) revealed the possible stabilization of high oxidation state metals in the center (metal having a degree of oxidation of 4 which could link covalently with four carbon atoms of the central ring) and/or the metallation of the external parts (metal having a degree of oxidation of 2 which could be linked to the nitrogens at the periphery of the macrocycle. The metal is for example tetracoordinated, pentacoordinated or hexacoordinated. Those compounds in their chelate form can be as following (le)-(li):

wherein:

R and R ² are defined as above,

Mi is chosen among the transition metals having a degree of oxidation of 4 and M ₂ is chosen among the transition metals having a degree of oxidation of 2 or lanthanides. Mi is preferably chosen among vanadium, titanium, iridium and platinum. M ₂ is preferably chosen among palladium, nickel, cobalt, zinc, iron, europium, cerium, gadolinium, lanthane;

Li and L ₂ , identical or different, is a monodentate, bidentate or tridentate ligand, preferably is a ligand which can give 1 covalent bond or 2 electrons, and/or may be optionally bound together. I_i and L ₂ can form together a group acac (L is O and the L and the two L are bound together), an amine, a phosphine, an aryl, or a halogen. It is also possible, in order to have tetraco ordinate, pentacoordinate or hexacoordinate that the complex comprises m L, m being chosen among 2 to 6.

The chelation of those metals can enable to improve the Eg gap of the molecules and also to absorb in infrared.

According to the present invention, the terms below have the following meanings: - an aromatic compound contains a set of covalently bound atoms with specific characteristics:

1 . A delocalized conjugated π system, most commonly an arrangement of alternating single and double bonds

2. A structure with all the contributing atoms of the aromatic ring in the same plane 3. Contributing atoms arranged in one or more rings

4. A number of π delocalized electrons that is 4n' + 2, where n' is an integer from 0 to 4.

In the present invention n' is 4;

- a halogen atom corresponds to a fluorine, chlorine, bromine or iodine atom;

- an alkyl group corresponds to a saturated, linear or branched aliphatic group having from 1 to 30 carbon atoms, preferably from 1 to 18 carbon atoms, for example from 1 to 10 carbon atoms.

- a cycloalkyl group corresponds to a cyclic alkyl group comprising from 3 to 6 members. The following examples may be cited: cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, etc;

- a heterocycle group is preferably a 5 to 10-membered cycle comprising at least one heteroatom, for example 1 , 2 or 3 heteroatoms, preferably chosen among N, S or O;

- an heteroaryl group corresponds to an aromatic heterocycle comprising from 5 to 10 members, preferably 5 or 6 members, preferably including from 1 to 3 heteroatoms preferably chosen among N, S or O;

- an aryl group corresponds to an aromatic cycloalkyl comprising from 6 to 10 members, preferably 6 members;

- a transition metal is an element from group 3 to group 12 and period 4 to period 7, except Lr and Lu, of the periodic table of the element;

- a lanthanide is an element of the periodic table having an atomic number from 57 through 71 .

It is understood that (R,), is such that for each of the j occurrence R, must be identical or different.

The compounds according to the present invention are surprisingly stable and could be exposed to air for months as a solid or for days in solution in DMSO without detectable changes. Without being bound to any theory, this high stability is not only due to aromatic behavior of the central ring but most likely to the zwitterionic character of the whole molecule.

Advantageously, the compounds of the invention absorb in all the visible, in UV and in the NIR region, especially between 300 and 1000 nm. Especially, the inventors have shown that the compounds of the invention absorb radiations around 880 nm which is in the NIR region. This specific range of absorbance especially enables to use those compounds in the field of electronics, photovoltaics, optoelectronics and photodynamic therapies. As mentioned above, the range of absorption can advantageously be modified by modifying the group R and R ² and/or by chelating metals.

Advantageously, the compounds of the invention present a Eg gap comprised between 0.5 and 4 eV, preferably between 1 and 4 eV. For example, compound of formula (I) wherein R and R ² represent H present a Eg gap of 1 .4 eV. This gap is determined by DFT calculations and by experiments (UV absorption) which is a technique well known by the skilled person. The Eg gap determined by electrochemical experiments is preferably of 1 .01 eV.

Without being bound to any theory, the inventors have found that the weak HOMO-

LUMO gap can be explained on one hand by the dianionic character of the central cycle and on the other hand by the similarity of the frontier molecular orbitals (HOMO and LUMO) which are totally delocalized. The value of this gap is important to determine the possible applications for the molecules. For example in order to be used in optoelectronics or photodynamic therapies, the gap has to be as low as possible.

The value of the gap should be modified by the modification of the group R and/or R ² making the compounds of formula (I) highly versatile. The value of the gap should also be modified by chelating compound of formula (I) with metal(s) as mentioned previously. The compounds of the invention present some electronic properties similar to the compounds disclosed by Qian et al (Chem. Asian. J., 2010, 5, 1006).

As a consequence, in view of their specific structural and electronic properties (especially due to their NIR absorbing properties) as well as their specific versatility, the compounds according to the invention can be used in many fields. For examples, the compounds of the invention could be used in electronics, more specifically in optoelectronics; in the field of photovoltaics; in the field of photonics; in the field of biology, especially in the field of photodynamic therapies.

Especially, when used in photovoltaics, the compounds of the invention having low dimensions and a weak Eg gap have different advantages compared to the polymers actually used: there are easy to synthesize, to functionalize (there are versatile), to purify... Since they absorb in all visible and partly in the NIR range, the compounds of the invention can be used alone in the photovoltaic cells and there is no need of different molecules as mentioned above. The compounds of the invention can thus be used as components of solar cells, including organic molecular cells, polymer cells and dye-sensitized solar cells. In those cells the compounds of the inventions serve as charge-transport agents and/or absorbing agents. As mentioned above, the compounds of the invention contain few atoms and absorb in the NIR region which make them good candidates for being used in photodynamic therapies for the treatment of cancer, including those in deep tissues. In photodynamic therapies, the compounds of the invention are used as photosensitizers. The compounds of the invention are very useful in such an application since they can be modified, by modifying the R and R ² group or by chelation, which enables to control the absorption range of the light as well as the solubility of the compounds.

The compounds of the invention could also be used as ligand in coordination chemistry since as mentioned above they can make chelate with metals.

The present invention also relates to the use of the compound of formula (I) in solar cells, particularly in organic solar cells and as dye in dye-sensitized solar cell such as Gratzel cell.

Indeed, due to their specific properties as mentioned above and especially the Eg gap and the properties of absorption of near IR, the compounds according to the invention are particularly useful as dye for dye-sensitized solar cell. Compounds of the invention where A is an aryl or heteroaryl, monocyclic or polycyclic, are particularly advantageous for the use in dye-sensitized cells especially due to the possible delocalisation of the charge after excitation of the compound by solar radiation.

According to the present invention dye-sensitized solar cell (Gratzel cell), intends to mean solar cells comprising two glass plaque defining an inner medium and one of them comprising a porous film of a semi-conductor, for example Ti0 ₂ , coated with a monolayer of a dye.

The present invention also relates to solar cell, the solar cell can be such as organic solar cells or dye-sensitized solar cells such as Gratzel cell, comprising a compound according to the invention. Preferably, the present invention relates to such as dye-sensitized solar cells, comprising two substrates defining an inner medium which comprises a semiconductor, for example Ti0 ₂ , and a compound of the invention as a dye.

The present invention also relates to a process (P1 ) for the preparation of compound of formula (I) when at least one of R or one of R ² is different from H comprising the following steps:

a1 ) reacting a 1 ,5-Q ₂ -2,4-dinitrobenzene with 0,5 equivalent of tetraaminobenzene in the presence of a base, Q, identical or different being a leaving group; reacting the compound obtained in step a1 ) with one equivalent of a compound derived from tetraaminobenzene in which at least one and at most two of NH ₂ group is substituted with a group R or R ² different from H, in the presence of a base;

reduction of the compound obtained in step b1 ) in the presence of a reducing agent which under air is converted into compound of formula (I).

The present invention also relates to a process (P2) for the preparation of compound of formula (I) when at least one of R or one of R ² is different form H comprising the following steps:

a2) reacting a 1 ,5-Q ₂ -2,4-dinitrobenzene with 1 equivalent of a compound derived from tetraaminobenzene in which at least one and at most two of NH ₂ group is substituted with a group R or R ² different from H, in the presence of a base, Q, identical or different being a leaving group;

b2) reduction of the compound obtained in step a2) in the presence of a reducing agent which under air is converted into compound of formula (I).

The present invention also relates to a process (P3) for the preparation of compound of formula (I) when at least one of R or one of R ² is different form H comprising the following steps:

a3) reacting a 1 ,5-Q ₂ -2,4-dinitrobenzene with 0,5 equivalent of a compound derived from tetraaminobenzene in which at least one and at most two of NH ₂ group is substituted with a first group R or R ² different from H, in the presence of a base, Q, identical or different being a leaving group;

b3) reacting the compound obtained in step a3) with one equivalent of a compound derived from tetraaminobenzene in which at least one and at most two of NH ₂ group is substituted with a second group R or R ² different from H and different from the one of step a3), in the presence of a base;

c3) reduction of the compound obtained in step b3) in the presence of a reducing agent which under air is converted into compound of formula (I).

Preferably, the reducing agent in process (P1 ), (P2) and (P3) is chosen among SnCI ₂ ; H ₂ , Pd/C; hydrazine; ammonium formate (NH ₄ ,HC0 ₂ ,Pd/C).

Preferably, the leaving group in process (P1 ), (P2) and (P3) is chosen among halides, triflates (OS0 ₂ CF ₃ ), sulfonate esters such as tosylate or mesylate. Preferably the leaving group is chosen among halides. Preferably 1 ,5-Q ₂ -2,4-dinitrobenzene is 1 ,5-difluoro-2,4- dinitrobenzene. Preferably, steps a1 ), b1 ), a2), a3) and c3) are carried out in the presence of a solvent, for example acetonitrile.

Preferably steps a1 ), b1 ), a2), a3) and c3) are carried out at low temperature, for example between -10 and 10°C, especially at 0 °C, tten the temperature is raised to room temperature, then, finally the reaction is carried out under reflux.

Preferably, in steps a1 ), b1 ), a2), a3) and c3) the base is for example diisopropylethylamine (DIPEA).

Preferably, in steps c1 ), b2) and c3), the reducing agent is used in large excess.

Preferably, in step c1 ), b2) and c3) can be implemented in the presence of an acid preferably for example when the reducing agent is SnCI ₂ , the acid is preferably HX, preferably HCI.

Preferably, steps d , b2 and c3) are carried out at a temperature of around 50-100 °C, for example 70 °C. Compounds of formula (la) and (lb) are obtained by reacting compounds of formula (I) with at least one mole of an acid.

Compounds of formula (lc) and (Id) are obtained by reacting compounds of formula (I) with at least one mole of a base.

Compounds of formula (le) to (li) are obtained by mixing compounds of formula (I) in solution in a solvent with the metal in solution in a solvent.

Advantageously, the synthetic accessibility to compounds of the invention is straightforward and highly versatile, as substituents on the peripheric nitrogen atoms are easily introduced and can be easily varied for tuning the properties of the compounds (solubility, geometry, donor/acceptor properties...)

The following examples describe the synthesis of some compounds according to the invention. These examples are not intended to be limitative and only illustrate the present invention. Example 1 : Preparation of compounds (1.1 ) and (1.2)

Step a1 ) Synthesis of Intermediate (a1 )

(a1 )

The commercially available 1 ,5-difluoro-2,4-dinitrobenzene was reacted with 0.5 equiv. of tetraaminobenzene in the presence of base (DIPEA) under inert atmosphere. The solution was stirred at 0 °C for 14 h and the resulting solid was isolated by filtration and washed affording (a1 ).

Step bp Synthesis of Intermediat and fb1 .2 R1 = CHPCOOH)

The triaryl derivative (a1 ) was reacted with 1 equiv. of disubstitued tetraaminobenzene - that could be prepared in two steps from 1 ,5-difluoro-2,4-dinitrobenzene and primary amines bearing COOH functions - in the presence of base (DIPEA) under inert atmosphere. The solution was stirred and the obtained solid was isolated by filtration and washed affording (b1 .1 ) or (b1 .2). Step c1 ) Synthesis of target (1 .1 R1 =C _K H ₄ C00H) or (1 .2 R1 = CHPCOOH)

Tetranitro-tetraaminoazacalixphyrins (b1 .1 ) or (b1 .2) were then reacted in the presence of reducing agent under inert atmosphere affording the corresponding octaamino- azacalixphyrins - not isolated - which under air are converted into azacalixphyrins respectively (1 .1 ) or (1 .2).

Example 2: Preparation of compounds (2.1) and (2.2)

Step a2) Synthesis of Intermediate (a2.1 R1 =C _K H ₄ C00H) or (a2.2 R1 = CHPCOOH)

The commercially available 1 ,5-difluoro-2,4-dinitrobenzene was reacted with 1 equiv. of disubstitued tetraaminobenzene - that could be prepared in two steps from 1 ,5-difluoro-2,4- dinitrobenzene and primary amines bearing COOH functions - in the presence of base (DIPEA) under inert atmosphere. The solution was stirred and the obtained solid was isolated by filtration and washed affording (a2.1 ) or (a2.2).

Steps b2) Synthesis of target (2.1 R1 =C _K H ₄ C00H) or (2.2 R1 = CHPCOOH)

Tetranitro-tetraaminoazacalixphyrins (a2.1 ) or (a2.2) were then reacted in the presence of reducing agent under inert atmosphere affording the corresponding octaamino- azacalixphyrins - not isolated - which under air are converted into azacalixphyrins respectively (2.1 ) or (2.2). Example 3: Preparation of compounds (3a) and (3b)

The commercially available 1 ,5-difluoro-2,4-dinitrobenzene was reacted with 0.5 equiv. of disubstitued tetraaminobenzene - that could be prepared in two steps from 1 ,5-difluoro-2,4- dinitrobenzene and primary amines bearing COOH functions - in the presence of base (DIPEA) under inert atmosphere. The solution was stirred and the crude product was purified by column chromatography (Si0 ₂ ) affording (a3.1 ) or (a3.2).

The triaryl derivatives (a3.1 ) or (a3.2) were reacted with 1 equiv. of dialkyltetraaminobenzene (5) - that could be prepared in two steps from 1 ,5-difluoro-2,4-dinitrobenzene and primary alkylamines - in the presence of base (DIPEA) under inert atmosphere. The solution was stirred and the crude product was purified by column chromatography (Si0 ₂ ) affording respectively (b3.1 ) or (b3.2). Step c3) Synthesis of target (3.1 R1 =C _K H ₄ C00H, R2=nBu) or (3.2 R1 = CHPCOOH, R2=nBu)

Tetranitro-azacalixphyrins (b3.1 ) or (b3.2) were then reacted in the presence of reducing agent under inert atmosphere affording the corresponding octaamino-azacalixphyrins - not isolated - which under air are converted into azacalixphyrins respectively (3.1 ) or (3.2).

Example 4 : Preparation of compounds (4a) and (4b) Step a4) Synthesis of Intermediate a4.1 (R1 =Octyl) or a4.2 (R1 = Butyl)

The commercially available 1 ,5-difluoro-2,4-dinitrobenzene (1 .8 eq.) was reacted with disubstitued tetraaminobenzene - that could be prepared in three steps from 1 ,5-difluoro-2,4- dinitrobenzene and primary alkyl amines - in degazed acetonitrile and in the presence of 8 eq. of base (DIPEA) added dropwise under inert atmosphere at 0 C. The reaction mixture was left at room temperature for another 10 hours. The crude product was precipitated in EtOH, recovered by filtration, washed several times with EtOH, and dried to afford the title compounds a4.1 and a4.2 with 70 % and 68% yield respectively. Step b4) Synthesis of Intermediate b4.1 (R1 =nOctyl. R2=C _R H ₄ COOH . R3= nBu) or b4.2 (R1 = nBu. R2=CRH ₄ COOH . R3= nBu)

alkylaryltetraaminobenzene - that could be prepared in three steps from 1 ,5-difluoro-2,4- dinitrobenzene with primary alkyl and arylamines - were reacted with 0.6 equiv of the triaryl derivatives (a4.1 ) or (a4.2) in degazed acetonitrile in the presence of 8 eq. of DIPEA. The solution was stirred at 70 C for 1 0 hours under inert atmosphere. The crude solution was concentrated under reduced pressure, the solid was taken up in EtOH and purified by filtration with several washings with DCM affording (b4.1 ) or (b4.2) with 30 % and 33% yield respectively.

Step c4) Synthesis of target 4a (R1 =nOctyl. R2=C _R H ₄ COOH . R3= nBu) or 4b (R1 = nBu. R2=CRH ₄ COOH . R3= nBu)

A solution of tetranitro-azacalixarenes b4.1 or b4.2 in MeOH/THF (3/1 , v/v) with a few drops of HCI was hydrogenated (P = 60 bars) in the presence of Pd/C (5%) for 24 hrs. The obtained octaamino-azacalixarenes - not isolated - are then oxydized under air and purified onto a celite pad previously washed with HCI in order to give azacalixphyrins 4a and 4b respectively with 80% yield.

Example 5: Preparation and photovoltaic measurement of a Gratzel cell

FTO conductive glass substrates (F-doped Sn0 ₂ ) were cleaned by successive sonication in soapy water, then an ethanolic solution of HCI (0.1 M) for 10 minutes, and finally dried in air. Ti0 ₂ films were then prepared in three steps. A first treatment is applied by immersion for 30 min in an aqueous TiCI ₄ solution at 80 °C. Three successive layers of mesoporous Ti0 ₂ were then screen printed with transparent colloidal paste (Dyesol DSL 18NR-T) and final light scattering (DSL 18NR-AO (Dyesol)) was affixed, with 20-minute long drying steps at 150°C between each layer. The obtained substrates were then sintered at 450 °C, following a progressive heating ramp (325°C for 5 min, 375°C f<D 5 min, 450°C for 30 min). A second TiCI ₄ treatment was immediately conducted afterwards and the electrodes were fired one last time at 450 °C for 30 minutes. Thicknesses were measured by a Sloan Dektak 3 profilometer and are in the range of 16 μηι. The prepared Ti0 ₂ electrodes were soaked while still hot (80 °C) in a 0.2 mM solution of the compound accordhg to the invention in a 1 :1 mixture (v:v) of dichloromethane and ethanol. After one night of dyeing, the electrodes were rinsed and dried in air, in the dark. Platinum based counter electrodes were prepared by drop casting two drops of hexachloroplatinic acid in distilled isopropanol (2 mg per ml) on FTO (fluorine tin oxide) plates, and subsequent firing at 380 °C for 30 minutes. The photoelectrode and the counter electrode were placed on top of each other and sealed using a thin transparent film of Surlyn polymer (DuPont, 60 μηι) as a spacer. The resulting chamber was filled with an iodine-based electrolyte (50 mM l ₂ , 0.4 M of lithium perchlorate, 0.1 M Lil, 0.6 M 1 -ethyl-2,3- dimethylimidazolium iodide in dry distilled acetonitrile) by vacuum back filling through a predrilled hole in the counter electrode, and the photovoltaic device was sealed afterwards with Surlyn and a cover glass. The cell had an active area of 0.25 cm ² . Photovoltaic measurements were performed with a calibrated AM 1 .5 artificial solar light simulator (Oriel) and a Keithley 2400 digital source-meter; data were collected with a local software designed by Synervia (labview). The overall conversion efficiency (η) of the photovoltaic cell is calculated from the integral photocurrent density (Jsc), the open-circuit photovoltage (Voc), the fill factor of the cell (FF), and the intensity of the incident light (IPh). The photovoltaic cell was illuminated with an Oriel lamp calibrated to AM 1 .5 (air mass) intensity (1000 W.m ^"2 ). The results are given below for compound 4a of example 4:

Clearly the azacalixphyrins 4a is an active component in dye-sensitized solar cell underscoring the potential of this class of dyes for this technology. The low photocurrent and photovoltage are ascribed to low electron injection driving force. However, the reducing properties of the excited-state can be enhanced upon introduction of electron releasing substituents on the azacalixphyrins core.