Electron spin resonance spectra of chloro(N-methyl-5,10,15,20-tetraphenyl-porphinato)copper(II) and manganese(II) complexes. Demethylation mechanism studies

The (o-p-o)-Terphenyl Embedded Calix[2]phyrin(2.2.1.1.1) and Its Cu(II) Complex

The introduction of a higher arene unit as a structural motif is unprecedented in calixphyrin chemistry. Herein, the syntheses, spectral and structural characterization of heretofore anonymous terphenylene unit (o-p-o) incorporated calixphyrin with fused sp2 meso carbons is reported. The explicitly tailored macrocyclic core is utilized to stabilize the Cu(II) metal ion. The molecular structures of the calixbenziphyrin and Cu(II) complex are unambiguously confirmed by single-crystal X-ray analysis. Moreover, theoretical supports uphold experimental conclusions.

Copper(II) complexes of inverted porphyrin and its methylated derivatives

The inverted porphyrins 2-aza-5,10,15,20-tetraphenyl-21-carbaporphyrin (CTPPH2) and its methylated derivatives 2-aza-2-methyl-5,10,15,20-tetraphenyl-21-carbaporphyrin (2-NCH3CTPPH) and 2-aza-2-methyl-5,10,15,20-tetraphenyl-21-methyl-21-carbaporphyrin (2-NCH3-21-CH3CTPPH) stabilize the rare organocopper(II) complexes (CTPP)CuII (1), (2-NCH3CTPP)CuII (2), (CTPPH)CuIIX (3-X), (2-NCH3CTPPH)CuIIX (4-X) (X = Cl-, TFA), and (2-NCH3-21-CH3CTPP)CuIICl (5). The EPR spectra recorded for 1, 2, 4, and 5 revealed typical features diagnostic of the copper(II) electronic structure. The superhyperfine coupling pattern indicates a presence of three nitrogen donors in the first coordination sphere. An addition of HX acid to 1 and 2 to yield the species 3-X and 4-X. The reaction mechanism includes protonation of the inner C(21) carbon accompanied by an axial coordination of anion. Methylation of (2-NCH3CTPP)CuII (2) with methyl iodide resulted in formation of (2-NCH3-21-CH3CTPP)CuIICl (5) which implies an existence of a sigma-carbanion-copper(II) bond in 2. The 2H NMR investigations carried out for the pyrrole deuterated derivatives (CTPP-d7)CuII, (2-NCH3-21-CH3CTTP-d7)CuIICl, and the methyl deuterated (2-NCH3-21-CD3CTPP)CuIICl one confirmed independently the copper(II) electronic structure with the considerable dx2-y2 metal orbital contribution to the SOMO. The redox properties of copper(II) inverted porphyrins were studied by the cyclic and differential pulse voltammetry. The halfwave potentials indicate a metal-centered oxidation of 1 (390 mV) and 2 (343 mV). The dimethylated homologue 5 reveals the reduction process at -224 mV attributed to the CuII/CuI transformation.