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.

A2B- and A3-Type Boron(III)Subchlorins Derived from meso-Diethoxycarbonyltripyrrane: Synthesis and Photophysical Exploration.

The first direct fabrication of A2B- and A3-type B(III)subchlorins from meso-ethoxycarbonyl-substituted tripyrrane has been realized by condensation with appropriate acid chlorides (benzoyl chloride, butyryl chloride, and ethyl chlorooxoacetate). The aliphatic acid chloride-based annulation reaction is new to subporphyrinoid chemistry. The phenyl (6a)- or n-propyl (6b)-substituted derivatives could be oxidized to the corresponding B(III)subporphyrins upon refluxing with DDQ, whereas the triethoxycarbonyl moiety (6c) was found to be resistant to oxidation and exhibits the most red-shifted absorption (587 nm) and emission (604 nm). The study indicates that absorption and emission behaviors of the B(III)subchlorin can be tuned by the introduction of electron-rich or electron-deficient substituents at the meso-position. B(III)subchlorins 6a and 6c generate singlet oxygen efficiently (44 and 40%, respectively) and, thus, may find application as potential photosensitizers in photodynamic therapy (PDT).

Meso-Free Boron(III)subchlorin and Its µ-Oxo Dimer with Interacting Chromophores.

Meso-free B(III)subchlorin 1 has been realized exclusively for the first time from meso-ethoxycarbonyl-substituted tripyrrane along with the first subchlorin dimer 2 as its µ-oxo analogue via a facile one-pot approach. The subchlorin is highly stable toward oxidation; hence, it was not contaminated with the corresponding subporphyrin analogue 3. The subchlorin (56%) and its dimer (30%) exhibit singlet oxygen generation ability for the first time. The B-O-B dimer displays strong exciton coupling between the two macrocycles.

Third-order nonlinear optical investigations of meso-tetrakis(2,3,5,6-tetrafluoro-N,N-dimethyl-4-anilinyl)porphyrin and its metal complexes.

We report here the experimental investigation on third-order nonlinear optical parameters of 5,10,15,20-tetrakis(2,3,5,6-tetrafluoro-N,N-dimethyl-4-anilinyl)porphyrin and its various metal complexes, using Z-scan technique at 532 nm. The third-order nonlinear optical susceptibilities (χ(3)) were of the order 10(-12) esu and are compared through degenerate four wave mixing (DFWM). The operating mechanism is reverse saturable absorption (RSA) as the effective excited-state absorption cross-section was found higher than ground state absorption cross-section as well as the magnitude of nonlinear absorption coefficient was found decreasing with on-axis input intensity. The compounds found to exhibit good optical limiting at 532 nm, 7 ns excitation steering applications in laser safety.