One- and two-photon absorption properties of two metalloporphyrin complexes

The linear and nonlinear optical properties of two metalloporphyrin complexes formed by the complementary coordination of central zinc or magnesium ions to the ligand 5, 10, 15-tri-（p-tolyl）-20-phenylethynylporphyrin are theo- retically investigated by using the analytic response theory at the density functional theory level. The results indicate that the studied complexes present more symmetric geometry structures than the ligand. The charge-transfer states of the two complexes in the lower energy region are all almost degenerate but those of the ligand are well separated. The ratio of the two-photon absorption cross sections of the ligand, zinc-porphyrin and magnesium-porphyrin com- plexes is 1.0：1.5：1.8, demonstrating that the two-photon absorption capability can be greatly increased when the ligand is coordinated with a metal ion. Moreover, several physical micro-mechanisms including electron transitions and in- tramolecular charge-transfer processes are discussed to explore the differences in optical property between the ligand and two complexes.

Chain-transfer-catalyst: strategy for construction of site-specific functional CO_(2)-based polycarbonates

Site-specific functional polymers are generally synthesized from functionalized chain transfer agents(CTA)in the presence of catalysts.However,the poor solubility or chemical inertness of CTAs may make polymerizations uncontrollable.Now,this issue is addressed by proposing a strategy of designing chain-transfer-catalyst(CTC)that combines catalyst and CTA into one.The occurrence of catalytic effect naturally triggers the chain transfer process to give catalyst-labeled polymers with well-defined structures.As a proof-of-concept,cobalt(III)porphyrin catalysts with one,two and four hydroxyl groups act as efficient CTCs,giving the corresponding site-specific functional poly(propylene carbonate)s(PPC),diversifying the topology of polymers.Furthermore,porphyrin-capped PPCs with controllable Mn in the range of 1,000–16,800 g mol^(-1)were obtained by using monofunctional CTC(CTCOH).Moreover,different from traditional“catalyst+CTA”systems,a novel dynamic network transfer mechanism of CTCOH was proposed.This study provides a CTC strategy for the synthesis of site-specific functional polymers.