Synthesis and high ranked NLT properties of new sulfonamide-substituted indium phthalocyanines

The synthesis and characterization of three new indium phthalocyanines bearing eight N-alkyl- or N-arylsulfonamide groups is described. The new compounds are {2,3,9,10,16,17,23,24-octakis4-(4-methoxyphenylaminosulfonyl]phenoxy]phthalocyaninato}indium(III) chloride (7), {2,3,9,10,16,17,23,24-octakis4-diethylaminosulfonyl)phenoxy]phthalocyaninato}indium(III) chloride (8) and {2,3,9,10,16,17,23,24-octakis4-didodecylaminosulfonyl)phenoxy]phthalocyaninato}indium(III) chloride (9), and were obtained in 23-49% yields. The precursors of phthalocyanines 7-9 are sulfonamide-substituted phthalonitriles that can be prepared by reacting 4,5-bis(4-chlorosulfonylphenoxy)phthalonitrile (3) with amines. The nonlinear transmission (NLT) of complexes 7-9 was determined at 532 nm using ns pulses. All three phthalocyanines behave as reverse saturable absorbers with increasing efficiency of optical limiting in the order 7 < 8 < 9. A comparative analysis of the NLT results is attempted in terms of the structural differences in 7-9.