Ying-Hui Zhang

Structural parameters and vibrational spectra of a series of zinc meso-phenylporphyrins: a DFT and experimental study.

The influences of meso-phenyl substitution on the geometric structure and vibrational spectra have been studied by DFT calculation (B3LYP/6-31G(d)) and experiment on a series of zinc porphyrins (ZnTPP: zinc 5,10,15,20-tetraphenylporphyrin; ZnTrPP: zinc 5,10,15-triphenylporphryin; ZnDPP: zinc 5,15-dipenylporphyirn; ZnMPP: zinc 5-monophenylporphyrin; ZnP: zinc porphine). Calculation indicates that meso-phenyl substitution gives rise to slight out-of-plane distortion but significant in-plane distortion, especially for the configuration around C(m) atom, to zinc porphyrin. The assignment of experimental vibrational spectra was proposed mainly on the basis of calculation. Different shifting tendency upon meso-phenyl substitution is observed for different structure-sensitive bands, such as the shifting of nu(2), nu(3), nu(6), and nu(8) modes toward higher frequencies and nu(4) and nu(28) modes toward lower frequencies, upon meso-phenyl substitution. This is attributed primarily to in-plane nuclear reorganization effect (IPNR), though the contribution from out-of-plane distortion cannot be excluded completely. Analysis on vibrational structure reveals that asymmetric meso-phenyl substitution, especially the 5,15-diphenyl substitution of ZnDPP, brings about asymmetric vibrational displacement, or even splitting of vibrational structure to normal modes involving mainly the motion of meso-C(m). This is ascribed to the reduction of symmetry of porphyrin skeleton caused by asymmetric meso-phenyl substitution.

Theoretical study of electronic structure and absorption spectra of diacid and zinc species of series of meso-phenylporphyrins.

DFT and TDDFT calculations with density functionals (PBE1PBE, B3LYP, and PBEPBE) have been employed in a study of HCl-acidified diacids of a series of meso-phenylporphyrins. This study aims to clarify the influence of conformational distortion, meso-phenyl substituents, and counterion Cl- on absorption spectra of porphyrin derivatives. Calculations indicate that all three factors increase the MOs level and decrease the Gouterman HOMO-LUMO gap; this, further, brings about the redshift of absorption band. In comparison with experimental methods, the PBE1PBE method produces a more credible description of UV-vis spectra than other two methods. TDDFT calculation with the PBE1PBE method indicates that the electronic effect of the meso-phenyl group is dominant for the spectral redshift of porphyrin diacid series as observed in zinc porphyrins. The redshift of the B band of porphyrin diacids is primarily caused by an electron-donating effect of the meso-phenyl group, whereas the Q band is more sensitive to the π electron delocalization effect. The counterion is indispensable in a theoretical study of electronic and spectral structure of porphyrin diacids.

Synthesis, spectral and theoretical studies on axial coordination of dinuclear Salen zinc(II) complexes

Two dinuclear chiral Salen Zn(II) complexes Zn2L (L = N,N′-(1R,2R)(−)-1,2-cyclohexylene-bis(3-hydroxybenzylideneimine)) and Zn2L′(OAc)2 (L′ = N,N′-(1R,2R)(−)-1,2-cyclohexylene-bis(3-methoxybenzylideneimine)) with compartmental, potentially hexadentate Schiff-base ligands L and L′ have been synthesized and characterized by elemental analyses, 1H NMR, mass spectra, UV–Vis spectra and circular dichroism spectra. Their axial coordination with N-containing monodentate ligand (imidazole) and bidentate bridging ligands (ethylenediamine and 1,2-propylenediamine) have been studied by circular dichroism spectral titration, UV–Vis spectral titration and molecular modeling. The results of thermodynamic study, including standard association constants (K θ), and thermodynamic parameters ( , , ), together with the energy obtained from molecular modeling suggest that Zn2L can bind two monodentate axial ligands or one bidentate ligand via a bridging mode with its two zinc atoms. However, the complex Zn2L′(OAc)2 can bind two bidentate ligands by a mode that each of its two zinc atoms coordinates to one of the two nitrogen atoms of the bidentate ligand. A small modification on the structure of a complex leads to a distinct binding mode with a certain ligand.

Rational Construction of Highly Tunable Donor–Acceptor Materials Based on a Crystalline Host–Guest Platform

Organic donor-acceptor systems have attracted much attention due to their various potential applications. However, the rational construction and modulation of highly ordered donor-acceptor systems could be a challenge due to the complicated self-assembly process of donor and acceptor species. Considering the well-defined arrangement of species at the molecule level, a crystalline host-guest system could be an ideal platform for the rational construction of donor-acceptor systems. Herein, it is shown how the rational construction of highly tunable donor-acceptor materials can be achieved based on a crystalline host-guest platform. Within the well-established metal-organic framework NKU-111 as the crystalline host enabled by the relatively stable coordination-directed assembly, the introduction and arrangement of guest molecules in the crystals allow the rational construction of the NKU-111⊃guest donor-acceptor system. The donor-acceptor interaction in the systems can be readily modulated with different guest molecules, which can be justified by the well-demonstrated guest-dependent characteristics. Accordingly, the NKU-111⊃guest reveals highly tunable donor-acceptor properties such as charge-transfer-based emissions and electrical conductivity. This work indicates the potential of crystalline host-guest systems as an ideal platform for systematic investigations of donor-acceptor materials.

Synthesis of chiral SalenZn(II) and its coordination with imidazole derivatives and amino acid ester derivatives

A chiral complex, SalenZn(II) (S), was synthesized and characterized. Its coordination with imidazole derivatives and amino acid ester derivatives was studied by UV-vis spectrophotometric titrations and CD spectroscopy. The binding constants decreased in the order K (Im)>K (2-MeIm)>K (2-Et-4-MeIm)>K (N-MeIm) for imidazole derivatives, and K (AlaOMe)>K (PheOMe)>K (ValOMe) for amino acid ester derivatives with the same configuration and K D >K L for amino acid esters with different configuration. CD spectra can quantify the strength of SalenZn(II)-ligand interactions, giving results consistent with the magnitudes of the binding constants. Moreover the minimum energy conformations of the adducts were obtained by simulated annealing, and quantum chemical calculations were performed based on those conformations to explain experimental results at the molecular level.