New Molecular Arrays Based on a Tin(IV) Porphyrin Scaffold

Abstract

Two new porphyrin arrays-a hexamer and a nonamer-have been synthesized and characterized by elemental analysis as well as mass, (1)H NMR, and UV-vis spectroscopic methods. The scheme of construction of these arrays employs a synthetic protocol involving sequential "organic" and "inorganic" reactions conducted, respectively, at the peripheral meso-phenyl ring and the central tin(IV) ion of the porphyrin scaffold. The architecture of the hexamer is such that it is based on a covalently linked tin(IV) porphyrin dimer, with each of the two tin(IV) centers trans-axially ligated to two free-base porphyrins, while the higher homologue features a tin(IV) porphyrin trimer as the basal unit, with its central metalloid ions having two free-base porphyrins as axial ligands. This extended, "axial-bonding"-type architecture of the new arrays has been investigated by the (1)H NMR method, which reveals characteristic ring-current-induced shifts and coupling patterns for the resonances due to protons of the axial free-base porphyrin subunits. The presence of any ring-ring (basal-basal, basal-axial, or axial-axial) interaction in these arrays is not obvious from their UV-vis and redox potential data, which are close to those of the corresponding constituent monomeric species. On the other hand, their singlet-state activities are quite different from those of the precursor reference compounds as probed by steady-state fluorescence. The results of the detailed investigations carried out on these hybrid, "bichromophoric" arrays have been interpreted in terms of the occurrence of intraarray, interchromophore energy- and electron-transfer reactions.

Tuning the optical properties of hyperbranched polymers through the modification of the end groups

“…The quantum efficiencies of 16a – 16d in toluene solutions were measured with a dilute solution of 9,10‐diphenylanthracene in toluene (quantum efficiency = 1.0) as the standard;65 all polymers exhibited moderate quantum efficiencies in solution. The quantum efficiency of 16e and 16f in toluene solutions was measured with a dilute solution of tetraphenylporphyrin (quantum efficiency = 0.11)36 and zinc tetraphenylporphyrin (quantum efficiency = 0.03) in toluene as the standard,66 respectively. The results are also summarized in Table 2.…”

Enhanced stokes shift of S2→S0 emission and structural investigations of Sn(IV)Porphyrins doped hybrid borate glasses

“…Since boric acid behaves as a strong acid in molten state, a part of Sn atom gets demetallated from the central core of the porphyrin and behaves like freebase porphyrin. The second lifetime ( 1 ) with major amplitude corresponding to the complexed form of Sn(IV)Porphyrins with two -BO 3 units axially and forms as a trimer similar to Sn(IV)Porphyrin trimer scaffolds [27]. The decrease in the short lifetime ( 1 ) for Sn(IV)THP and Sn(IV)TPPCl 4 indicates that in addition to axial coordination peripheral coordination also occurs in these molecules.…”

Tin(IV)-Porphyrin Tetracarbonyl Cobaltate: An Efficient Catalyst for the Carbonylation of Epoxides

“…Among those complexes, tin(IV) porphyrins have attracted our attention. Since the first synthesis of tin(IV) porphyrin in 1948 by Rothemund, a wide range of tin-based porphyrins have been developed [27][28][29][30][31][32][33]. As catalysts, they mediate hydrolysis [34], acetylation [30,31], alcoholysis [32], and epoxide ring-opening reactions [26], as well as polymerizations [26,28].…”