Facile synthesis, spectroscopic and electrochemical properties, and theoretical calculations of porphyrin dimers with a bridging amide-bonded xanthene moiety

Abstract

A free base porphyrin dimer bridged by a flexible amide-bonded xanthene moiety and its binuclear zinc(II) complex zinc(II) complex were synthesized and characterized. Structural characterization by MS and 1 H NMR spectroscopy confirmed the bridged porphyrin dimer structure. The properties of the dimers were characterized by IR, UV-visible absorption, fluorescence and magnetic circular dichroism (MCD) spectroscopy, and electrochemistry studies. Theoretical calculations were carried out to analyze the electronic structures of porphyrin dimers with a bridging amide-bonded xanthene moiety.

Spectroscopic investigations and theoretical calculations of DABCO induced xanthene bridged self-assembled zinc(II) porphyrin dimer

“…Large red diamonds are used to denote the Q and B-bands of Gouterman's 4-orbital model [16] and smaller gray and green diamonds are used to denote charge transfer bands between the two porphyrin rings and higher energy porphyrin p-p* bands, respectively Q(0, 0), Q(0, 1) and B(0, 0) bands at 597, 556 and 420 nm. As was reported previously [12], it is noteworthy that the B-band signals are significantly less symmetrical than those typically observed for Zn(II) tetraphenylporphyrins [18]. Molecular modeling calculations made it obvious that the flexible amide bonds enable access to a wide range of conformations in which the two porphyrin rings are not in a cofacial arrangement.…”

“…The preparation of the xanthene-bridged amide-bonded Zn(II) porphyrin dimer shown in Scheme 1 was carried out according to the literature [12]. A series of titrations were carried out to study changes in the spectroscopic properties of 5 as DABCO (0~1.0 eq.)…”

“…3.0 Å [15]. Since the xanthene bridge does not contain a conjugated p-system, this results in very weak p-p* interactions between the two porphyrin rings, the MOs are still effectively localized porphyrin ring as a monomer (Figs 3 and 4) [12]. A narrowing of the HOMO-LUMO gap is predicted due to a slight relative destabilization of the s MO (a 2u under D 4h symmetry) of the porphyrin ring, which has large MO coefficients on the pyrrole nitrogens and hence is most likely to be affected by changes in the axial ligation of the Zn(II) ions.…”

Bio-Inspired Ni(II) Porphyrin Dimers with a Bridging Diphenyl Moiety: Facile Synthesis and Molecular Inherent Chirality

“…[23] In addition, when theoretical calculations were carried out on the Zn(II)porphyrin dimer complex, large separations were correctly predicted between the two porphyrin rings for different possible conformations of the flexible amide-linked derivatives, and hence there was no scope for a significant interaction between the rings. [24] When Ni(II) porphyrin dimers were prepared containing both amidebond and functional building blocks, even when empirical dispersion corrections were applied, the smaller distance was preferable to predict the arrangement of the porphyrin rings in the B3LYP-optimized structures with lower molecular ground state. [21] Thus, Ni(II)porphyrin dimers maybe the suitable candidates to simplify the current system to investigate the synthesis and properties of inherently chiral porphyrin dimers.…”

Flexible Metal–Porphyrin Dimers (M=MnIIICl, CoII, NiII, CuII): Synthesis, Spectroscopy, Electrochemistry, Spectroelectrochemistry, and Theoretical Calculations

“…When calculations were previously carried out on the Zn II dimer complex, large separations were predicted between the two porphyrin rings for different possible conformations of the flexible amide‐linked xanthene bridge, and hence there was no scope for a significant interaction between the rings. In the context of 5 c and 5 d , even when empirical dispersion corrections were applied so that a smaller distance was predicted between the porphyrin rings in the B3LYP‐optimized structures (Figure ), only a relatively minor interaction was predicted between the two chromophores.…”