-
[show abstract]
[hide abstract]
ABSTRACT: Two examples of supramolecular tetrads containing Sn(IV) porphyrin, expanded thiaporphyrins such as sapphyrin and rubyrin, and Ru(II) porphyrin assembled using non-interfering cooperative tin(IV)-oxygen and ruthenium(II)-nitrogen coordination properties are described. These are the first examples in which the expanded porphyrins are used as axial ligands. The tetrads were prepared by adopting one step as well as stepwise approaches. In a one pot approach, the mono meso-pyridyl dihydroxy Sn(IV) porphyrin, meso-hydroxyphenyl expanded thiaporphyrin, and Ru(II) porphyrin were reacted in benzene under refluxing conditions followed by column chromatographic purification on alumina to afford tetrads. In a stepwise approach, the axial bonding type of triads containing Sn(IV)porphyrin as central unit and expanded thiaporphyrins as axial ligands were synthesized first by reacting meso-pyridyl dihydroxy Sn(IV) porphyrin with meso-hydroxyphenyl expanded thiaporphyrin in benzene at refluxing temperature. In the next step, the triads were reacted with Ru(II) porphyrin under mild reaction conditions to afford tetrads in decent yields. Both methods worked efficiently and produced stable, soluble tetrads in decent yields. One-dimensional (1D) and two-dimensional (2D) NMR techniques were used to confirm the identity of these novel tetrads. Absorption and electrochemical studies indicated that the components in tetrads interact weakly and retain their individual characteristic features. The steady state photophysical studies revealed that the quantum yield of Sn(IV) porphyrin in tetrads was reduced significantly because of non-radiative decay pathways operating in these systems.
Inorganic Chemistry 01/2011; 50(5):1713-22. · 4.60 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The first examples of stable 22-thiacorroles containing a direct pyrrole-pyrrole bond were synthesized using thiophene monocarbinols as key precursors. Condensation of 1 equiv of thiophene monocarbinol with 1 equiv of substituted aldehyde and 1.5 equiv of pyrrole under refluxing propionic acid conditions followed by alumina column chromatographic purification yielded the desired 22-thiacorroles. Although the corrole formation had been observed with variety of substituted aldehydes, the stable thiacorroles were isolated in 2-3% yields only with 4- and 3-nitrobenzaldehydes. The stable thiacorroles were obtained only under harsh propionic acid conditions and any other mild reaction conditions did not yield 22-thiacorroles. The structure of thiacorroles were unambiguously established using mass, and 1D and 2D NMR spectroscopy. The NMR study indicated diminished ring current and distortion of 22-thiacorroles. DFT studies also supported the distortion of thiacorroles. The absorption spectra showed reduction in number of absorption bands and fluorescence study indicated that 22-thiacorroles are weakly fluorescent. The electrochemical studies indicated that 22-thiacorroles undergo easier reductions compared to thiaporphyrins.
The Journal of Organic Chemistry 06/2010; 75(12):4172-82. · 4.45 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The thiaporphyrin building blocks with N(3)S and N(2)S(2) cores containing one hydroxyphenyl functional group at the meso position were synthesized by adopting the unsymmetrical thiophene diol method. These monohydroxy thiaporphyrins were used to construct the first examples of axial bonding type Sn(IV) porphyrin triads in which Sn(IV) porphyrin acts as basal unit and the two thiaporphyrin units as axial ligands by treating with SnTTP(OH)(2) in benzene at refluxing temperature. The axial bonding type triads were confirmed by mass, 1D and 2D NMR studies. The absorption and electrochemical studies support weak ground state interaction among the porphyrin subunits within the porphyrin triads. The fluorescence studies indicate there is a possibility of energy transfer at the singlet state from basal Sn(IV) porphyrin unit to axial thiaporphyrin units.
Inorganic Chemistry 02/2010; 49(6):2692-700. · 4.60 Impact Factor
-
Annalen der Chemie und Pharmacie 12/2009; 2010(3):494 - 508. · 3.10 Impact Factor
