Rare earth complex excellent in thermal resistance

A multinuclear rare earth complex formed by coordinating one or more types of molecules having a photosensitizing function and a vibrational energy quenching-suppressing function to a plurality of rare earth ions, which is represented by the general formula:

• LpL′q(Ln)rXs,
• wherein
• L is a ligand having a photosensitizing function represented by the general formula:
• wherein R1, R2, R3, R4 and R5 are independently hydrogen, a hydroxide group, a substituted or unsubstituted amino group, a substituted or unsubstituted aryl group, a nitro group, a cyano group, an alkyl group or a cycloalkyl group represented by —R, an alkoxy group represented by —OR, or an acyl group represented by —C(C═O)R, where R is a substituted or unsubstituted alkyl group or cycloalkyl group having a carbon number of 1 to 20;
• Y1 is —OH;
• and
• Y2 is ═O;
• is an integer of 1 to 40;
• L′ is a ligand which is a hydroxide ion;
• q is an integer of 0 to 8;
• Ln is a rare earth ion;
• r is an integer of 2 to 20, where a plurality of Ln may be different from each other;
• X is O, —OH, S, —SH, Se or Te;
• s is an integer of 1 to 20, where a plurality of X may be different from each other when s is an integer of 2 to 20;
• and further, the integers p, r and s have a relationship indicated by the expression:
• 1≦p/r≦4, 1≦r/s≦4 [expression 1]
• wherein a coordination manner of L to Ln is:
• Coordination Manner (A) where both Y1 and Y2 bind to the identical Ln;
• Coordination Manner (B) where Y1 and Y2 bind to different Ln each other;
• and a combination thereof, wherein when Y1 coordinates to Ln, a proton leaves from —OH represented by Y1 to form —O—, thereby L coordinates to Ln via —O—.