Construction of Novel Cyclic Tetrads by Axial Coordination of Thiaporphyrins to Tin(IV) Porphyrin

Abstract

We report the formation of new cyclic porphyrin tetrads 1 and 2, which were obtained from the reaction between dihydroxytin(IV) porphyrin and cis-dihydroxy-21-thiaporphyrin/21,23-dithiaporphyrin. The unique oxophilicity of tin(IV) porphyrin was the driving force for the formation of these tetrads. Moreover, these novel tetrads represent the first examples of cyclic porphyrins containing tin(IV) that are constructed exclusively on the basis of the "Sn-O" interaction without any other complementary, noncompetitive mode of interactions. The molecular structures of the cyclic tetrads have been investigated by matrix-assisted laser desorption ionization time-of-flight mass spectrometry, NMR spectroscopy, quantum-mechanical calculations, and, in one case, single-crystal X-ray crystallography. The X-ray structure revealed that the two cis-dihydroxy-NS porphyrins were coordinated at the axial positions of two tin(IV) porphyrins, leading to the symmetric cyclic tetrad structure. The optical properties of tetrads were studied, and these compounds were stable under redox conditions. Preliminary photophysical studies carried out on the tetrads indicated efficient energy transfer from tin(IV) porphyrin to the thiaporphyrin unit, which highlights their potential applications in energy and electron transfer in the future.

Sn(IV) Multiporphyrin Arrays as Tunable Photoactive Systems

“…An ultrafast photophysical investigation revealed that, in these systems, photoinduced electron and/or energy transfer processes can occur. An elegant and interesting study on cyclic porphyrins tetrads was done very recently by the Ravikanth group . These supramolecular systems were obtained by axial coordination of thiaporphyrins to Sn­(IV) porphyrins exclusively on the basis of the “Sn–O” phenolate axial bonds.…”

“…An elegant and interesting study on cyclic porphyrins tetrads was done very recently by the Ravikanth group. 26 These supramolecular systems were obtained by axial coordination of thiaporphyrins to Sn(IV) porphyrins exclusively on the basis of the "Sn−O" phenolate axial bonds. A preliminary photophysical study indicated that an efficient energy transfer process occurs from the Sn(IV) porphyrin to the thiaporphyrin units.…”

(trans-Dihydroxo)Sn(IV)-[5,10,15,20-tetrakis(2-pyridyl)porphyrin]

“…Here, we report a tin(IV) porphyrin complex with trans-dihydroxo axial-ligand and 2-pyridyl peripheral substituents, namely, (trans-dihydroxo) [5,10,15,20-tetrakis(2-pyridyl)porphyrinato]tin(IV). Cooperativities between axial ligands and peripheral functional groups in six-coordinated Sn(IV)-porphyrins can lead to various assembled structures for the development of interesting porphyrin materials [20][21][22][23][24][25][26][27][28][29][30].…”