To obtain a new compound comprising a specific methine compound having a nitrogen-containing heterocyclic ring, high in stability, large in dyeability, and useful as a dyestuff for filters, a dyestuff for dyeing pulp, a dyestuff for photographilic sensitive materials, a spectral sensitive dyestuff, as a medicine, etc.

A new methine compound represented by the formula [Z] is a non-metallic atom group required for completing the formation of a five or six-membered nitrogen-containing heterocyclic ring; R1 is a (substituted) alkyl; R2 is an alkyl or alkenyl having at least one carboxyl group and at least one ester bond, amide bond or ether bond, etc.; X1 is a counter ion required for neutralizing an electric charge; n1 is a number of 0 or larger which is required for neutralizing the electric charge in the molecule]. The compound is high in stability, large in dyeability, and useful as a dyestuff for filters, a dyestuff for dyeing pulp, a dyestuff for photographic sensitive materials, a spectral sensitive pigment for photography, a medicine, etc. The compound is obtained by synthesizing a merocyanine dyestuff having a rhodanine ring substituted with a nucleophilic functional group and subsequently reacting the product with an electrophilic compound.