On the Jahn-Teller Effect in Silver Complexes of Dimethyl Amino Phenyl Substituted Phthalocyanine.

The structures of Ag complexes with dimethyl amino phenyl substituted phthalocyanine m [dmaphPcAg] q of various charges q and in the two lowest spin states m were optimized using the B3LYP method within the D 4h symmetry group and its subgroups. The most stable reaction intermediate in the supposed photoinitiation reaction is 3 [dmaphPcAg] - . Group-theoretical analysis of the optimized structures and of their electron states reveals two symmetry-descent mechanisms. The stable structures of maximal symmetry of complexes 1 [dmaphPcAg] + , 3 [dmaphPcAg] + , 2 [dmaphPcAg] 0 , and 4 [dmaphPcAg] 2- correspond to the D 4 group as a consequence of the pseudo-Jahn-Teller effect within unstable D 4h structure. Complexes 4 [dmaphPcAg] 0 , 1 [dmaphPcAg] - , 3 [dmaphPcAg] - , and 2 [dmaphPcAg] 2- with double degenerate electron ground states in D 4h symmetry structures undergo a symmetry descent to stable structures corresponding to maximal D 2 symmetry, not because of a simple Jahn-Teller effect but due to a hidden pseudo-Jahn-Teller effect (strong vibronic interaction between excited electron states). The reduction of the neutral photoinitiator causes symmetry descent to its anionic intermediate because of vibronic interactions that must significantly affect the polymerization reactions.