Synthesis, spectroscopic properties and electrochemistry of (2,9,16,23-tetrasubstituted phthalocyaninato) erbium complexes

Two homoleptic bis(phthalocyaninato) erbium(III) complexes Er[Pc(β-OR/R)4]2 and two half-sandwich phthalocyaninato erbium(III) complexes (acac)Er[Pc(β-OR/R)4] (OR = 1-n-pentyloxy and R = tert-butyl) have been synthesized and characterized by MALDI-TOF-MS as well as by various spectroscopic methods. The introduction of different substituents (alkoxy or alkyl groups) to the phthalocyanine rings induced changes in the spectroscopic and electrochemical properties. Although the excited states of the homoleptic double- and triple-decker complexes usually are considered to lack fluorescence, in these cases, the homoleptic bis(phthalocyaninato) erbium(III) complexes Er[Pc(β-OR/R)4]2 displayed intense fluorescence compared with the half-sandwich phthalocyaninato erbium(III) complexes (acac)Er[Pc(β-OR/R)4]. For the two kinds of phthalocyaninato erbium(III) complexes, the pentyloxy-substituted complexes gave relatively intense emission compared with the tert-butyl-substituted complexes. These differences in the electronic ground state absorptions and in the excited state properties correlate with observations made from electrochemical measurements.