Hua-Hua Wang

Crystal structure, magnetic and catalytic oxidation properties of manganese(III) tetrakis(ethoxycarbonyl)porphyrin

A new meso-tetraalkyl porphyrin manganese complex, 5,10,15,20-tetrakis(ethoxycarbonyl)porphyrinatomanganese (MnIIITECPCl), had been prepared and characterized by X-ray structure determination. MnIIITECPCl exists as a coordinated dimer in its crystal structure with a weak antiferromagnetic coupling between two Mn(III) ions. The catalytic oxidation of styrene by MnIIITECPCl was carried out in acetonitrile. MnIIITECPCl was found to be recyclable with a high conversion efficiency when using TBHP as an oxidant and the major product was benzaldehyde. MnIIITECPCl was also reusable by using an PhIO oxidant, but the major products turned out to be phenyl acetaldehyde and styrene epoxide.

Copper porphyrin catalyzed esterification of C(sp3)–H via a cross-dehydrogenative coupling reaction

The crystal structure of 5,10,15,20-tetra(ethoxycarbonyl)porphyrin copper(II) showed that its central copper has a six-coordinate structure. An efficient copper porphyrin-catalyzed cross-dehydrogenative coupling (CDC) esterification reaction between C(sp3)–H and carboxylic acids using di-tert-butyl peroxide (DTBP) as an oxidant was established. The kinetic isotope effect (KIE) indicated that C(sp3)–H bond cleavage was the rate-determining step of this CDC reaction.

Oxygen atom transfer reactions from sterically encumbered brominated (oxo)manganese(V) corroles to styrene

Seven A3- and trans-A2B manganese(III) corroles (1–7-Mn) differing widely in their electronic and steric features were synthesized and transformed to their corresponding β-brominated manganese(III) corroles derivatives (1a–7a-Mn). Their corresponding (oxo)manganese(V) corroles 1–7-Mn(oxo) and 1a–7a-Mn(oxo) were further prepapred by treating with iodosylbenzene (PhIO). The reactivity for the oxygen atom transfer from 1–7-Mn(oxo) to styrene followed the order of 1-Mn(oxo) > 2-Mn(oxo) > 7-Mn(oxo) > 4-Mn(oxo) > 3-Mn(oxo) > 6-Mn(oxo) ≈5-Mn(oxo). The same pattern was observed for their β-brominated analogs 1a–7a-Mn(oxo), albeit their reactivity was remarkably higher. The steric protection of MnV ≡O moiety by ortho–ortho′-dibromophenyl substituents was found to enhance the stability of (oxo)manganese(V) corroles significantly.

DNA-binding, photocleavage and anti-cancer activity of tin(IV) corrole

A new tin(IV) corrole, 5,10,15-tris(4-methoxycarbonylphenyl) corrole tin(IV) (1-Sn) was synthesized and characterized. The DNA binding, photocleavage and anti-cancer activity were studied and compared with its free-base. The interaction of 1-Sn and its free-base 1 with calf thymus DNA had been investigated by spectroscopic methods, viscosity measurements and molecular docking analysis. The results revealed that 1-Sn and 1 could interact with calf thymus DNA via an outside groove binding mode. Furthermore, although 1 displayed no photonuclease activity, 1-Sn exhibited good photonuclease activity as indicated by agarose gel electrophoresis, and superoxide anion might be the active intermediate for the DNA scission. Finally, 1 was nontoxic but 1-Sn displayed cytotoxicity towards A549 tumor cell lines.

Porphyrin–Coumarin Dyads: Investigation of Photophysical Properties and DNA Interactions

Two new nonconjugated porphyrin-coumarin dyads with different orientations with respect to donor-acceptor entities and their zinc complexes were synthesized. Single-crystal structures of the free-base porphyrin-coumarin dyads were successfully resolved. The absorption spectra of the dyads were linear combinations of the spectra of their corresponding monomers, indicating a negligible electronic communication between the coumarin and porphyrin moieties. However, the fluorescence emission of the coumarin entity in all of the dyads was quenched significantly compared to that of pristine coumarin, and this effect was attributed to intramolecular energy transfer from the coumarin to the porphyrin. The energy transfer kinetics from the coumarin to the porphyrin was shown to be fast ( kFörster = 1.13 × 1013 s-1 for the ortho-isomer and 5.13 × 1011 s-1 for the para-isomer in DMF) and efficient (transfer efficiency ca. 96-97%). Transient absorption studies showed that the excited state decay process (S2 → S1*, S1* → S1, S1 → S0, and S1 → T1) of the para-isomer was faster than that of the ortho-isomer in DMF. All of the synthesized dyads were tested for their interactions with ct-DNA and photocleavage activity toward PBR322-DNA. The results revealed that all of the dyads interacted with ct-DNA via only an external groove-binding mode; the binding constants were calculated to be 3.24 × 105 (3a), 3.05 × 105 (3b), 3.04 × 105 (4a), and 4.88 × 105 (4b), and the photocleavage activity was in the order 4b < 3b < 4a < 3a. Furthermore, only the zinc complexes of the porphyrin-coumarin dyads could be absorbed by tumor cells (A549). These complexes were mainly localized in the cytoplasm, exhibited red fluorescence, and showed low cytotoxicity toward all of the tumor cell lines tested. The results showed that these zinc complexes of the porphyrin-coumarin dyads have potential applications in fluorescence imaging.