Effect of ß-Substitution and ß,ß'-Fusion on the Formation of Boron Complexes of Porphycenes.

Boron(III) complexation was investigated in a series of ß-substituted porphycenes. Unlike meso-arylporphycenes, these macrocycles undergo a facile complexation reaction. Upon fusion of the ß,ß'-positions of the porphycene ligand, the complexation resulted in fast insertion of boron, forming the cisoid-B2OF2 complex. However, in the case of the other ß-substituted porphycenes, only bis-BF2 complexes formed. The effect of these substituents on the core geometry and photophysical properties are elaborated here.

Monothia [22]pentaphyrin(2.0.1.1.0): a core-modified isomer of sapphyrin.

A novel 22π-aromatic sapphyrin isomer endowed with an acene moiety was designed and realised for the first time as a core-modified monothia analogue. This macrocycle exhibited absorption and emission in the near-infrared region. It was diprotonated under strongly acidic conditions and bound to anions like sapphyrin. It showed unusual coordination chemistry, acting as a neutral ligand and undergoing large out-of-plane deformation to bind Pd(II) ions.

In-Core N4-Coordination of Palladium(II) in Dinaphthoporphycene: Synthesis, Structure, and Photophysical Studies.

Dinaphthoporphycene (DNP) has emerged as a versatile ligand undergoing large out-of-plane distortion to form a cis-bimetallic complex with Pd(II) using Pd(OAc)2 and out-of-plane monometallic complexes with Pd(acac)2 and PtCl2(PhCN)2. Herein, we are finally able to synthesize the in-core complex with Pd(II) using PdCl2(PhCN)2 or PdCl2. The crystal structure shows the palladium ion resides slightly above the N4-core, with the Pd(II) dimensionally dissenting with the typical square planarity displayed by the reported in-core DNP complexes with Ni(II) and Cu(II) ions. The deformed complex displays a blue shift in the absorption spectra compared to DNP and its metallo-derivatives. PdDNP exhibits a moderate singlet oxygen generation ability (18%).

3,6,13,16-Tetrapropylporphycene: Rational Synthesis, Complexation, and Halogenation.

We have designed and synthesized 3,6,13,16-tetrapropylporphycene for the first time as its alkyl analogue from ethyl 4-propyl-1H-pyrrole-2-carboxylate. The substituent effect was found to be more intense than reported positional isomeric tetrapropylporphycenes. The freebase porphycene exhibited moderate fluorescence and complexation ability with divalent metal ions, including Zn(II), which displayed an enhanced emission quantum yield (∼30%). The Pd(II) complex and freebase ß-tetrabromoporphycene generated singlet oxygen efficiently (75 and 51%, respectively) and, hence, may find application as potential photosensitizers in photodynamic therapy.