Metal-containing azo compound and optical recording media

A metal-containing azo compound represented by at least one formula which is selected from the following general formulae (a1), (a2), (a3) and (a4):

• wherein M(II) is a bivalent metal, each of X1 and X2 is a substituted or non-substituted residue that forms a monocyclic or polycyclic aromatic ring together with carbon atoms that are adjacent thereto at its both ends, each of Y1 and Y2 is a substituted or non-substituted residue that forms a nitrogen-containing aromatic heterocycle together with a nitrogen atom and carbon atoms that are adjacent thereto at its both ends, and a substituent when present in the residue is independently selected from the group consisting of a halogen atom, a substituted and non-substituted alkyl group, a substituted and non-substituted alkoxyl group, a substituted and non-substituted alkylthio group, a substituted and non-substituted aryl group, a substituted and non-substituted aryloxyl group, a substituted and non-substituted arylthio group, a nitro group, and a substituted and non-substituted amino group, and one residue is different from the other in at least one of a combination of X1 and X2 and a combination of Y1 and Y2;
• the compound includes substituents R1 and R2 which are bonded respectively to carbon atoms adjacent to the residues Y1 and Y2 respectively;
• R1 and R2 are each selected from the group consisting of a hydrogen atom, a substituted and non-substituted alkyl group having 1 to 9 carbon atoms, a substituted and non-substituted alkoxyl group having 1 to 9 carbon atoms, a substituted and non-substituted alkylthio group having 1 to 9 carbon atoms, a substituted and non-substituted aryl group having 6 to 9 carbon atoms, a substituted and non-substituted aryloxyl group having 6 to 9 carbon atoms, and a substituted and non-substituted arylthio group having 6 to 9 carbon atoms;
• when one of R1 and R2 is a hydrogen atom, the other is not a hydrogen atom;
• and
• at least one of a combination of the residues X1 and X2, a combination of the residues Y1 and Y2, and a combination of substituents R1 and R2, the residues or the substituents are different from each other.