Metal-Mediated CH Bond Activation in a Carbon-Substituted Hemiporphyrazine

Structural Diversity and Rare η1 Cu-C Interactions in CuI Complexes of 1,2,3-Triazole-Functionalized Bisphosphines

This manuscript describes the synthesis of copper complexes of 1,2,3-triazolyl-phosphines: o-Ph2P(C6H4){1,2,3-N3CC6H5)C(PPh2)} (L1), (C6H5){1,2,3-N3C(C6H4(o-PPh2))-C(PPh2)} (L2), 3-Ph2P(C5H3N){1,2,3-N3C(C6H5)C(PPh2)} (L3), o-Ph2P(C6H4){1,2,3-N3C(C5H5N)C(PPh2)} (L4), and {(3,5-Ph2PC6H4-o)21,2,3-N3CCH} (L5). The reactions of L1-L3 with CuI salts afforded dimeric complexes having the general formula [Cu2(μ -X)2L2] (L = L1, X = Cl, Br and I: 1 - 3; L= L2, X = Cl, Br and I: 4- 6; L = L3; X = Cl, Br, and I: 7-9). The reaction of L4 with CuI in a 1:2 molar ratio afforded 1D-coordination polymer [{(CuI)2{o-Ph2P(C6H4){1,2,3-N3C(C5H5N)C(PPh2)}-μ-((k1-N)(k2-P,P))}}]n (10). The reaction of L5 with cuprous halides (CuX) (X = Br, I) yielded mononuclear complexes [CuX{(3,5-Ph2PC6H4-o)21,2,3-N3CCH}-κ2P,P] (X = Br, 12; I, 13). Crystal structures of complexes 12 and 13 showed close interactions between CuI and the triazole C7 carbon. These relatively short Cu···C7 separations may be due to the η1-C interaction (dπ-pπ bond) between the triazolic carbon atom (via pz orbital) and CuI or three-centered two-electron interaction between CuI and the triazolic C-H bond. The existence of the Cu···C interaction was further evinced by the QTAIM analysis in compounds 12 and 13.

A Switchable Near-Infrared-Absorbing Dye Based on Redox-Bistable Benzitetraazaporphyrin

Activatable near-infrared (NIR) dyes responsive to external stimuli are used in medical and other applications. Here, we describe the design and synthesis of bench-stable 18π- and 20π-electron benzitetraazaporphyrins (BzTAPs) possessing redox-switchable NIR properties. X-Ray, NMR, and UV/Visible-NIR analyses revealed that 20π-electron BzTAP 1 exhibits NIR absorption and antiaromaticity with a paratropic ring-current, while 18π-electron BzTAP 2 shows weakly aromatic character with NIR inertness. Notably, the NIR-silent BzTAP 2 was readily converted to the NIR-active BzTAP 1 in the presence of mild reducing agents such as amine. The intense NIR absorption band of BzTAP 1 is in sharp contrast to the very weak absorption bands of previously reported antiaromatic porphyrinoids. Molecular orbital analysis revealed that symmetry-lowering perturbation of the 20π-electron porphyrinoid skeleton enables the HOMO-LUMO transition of 1 to be electric-dipole-allowed. BzTAPs are expected to be useful for constructing activatable NIR probes working in reductive environments.

N-Substituted Azacalixphyrins: Synthesis, Properties, and Self-Assembly

Pre- and postintroduction of substituents with respect to the macrocyclization step leads to previously unknown N-substituted azacalixphyrins. The stepwise synthetic approach has been studied in detail to highlight the key role of the N-substituents of the precursors and/or intermediates in terms of reactivity. Based on a combined experimental and theoretical investigation, the relationship between the properties of the macrocycles and their degree of substitution is rationalized. Depending on the nature of the N-substituents, the formation of supramolecular ribbon-like structures could also be observed, as demonstrated by combined TEM, SEM, AFM, and FTIR experiments.

A Chiral Hemiporphyrazine Derivative: Synthesis and Chiroptical Properties

The synthesis of an optically active hemiporphyrazine with chiral binaphthyl substituents (1) is reported, providing the first example of the incorporation of an intrinsically chiral moiety into the macrocyclic core of a hemiporphyrazine analogue. A negative circular dichroism (CD) signal is observed in the 325-450 nm region of the CD spectrum of (S,S)-1, while mainly positive bands are observed in the 220-325 nm region. Mirror symmetry is observed across the entire wavelength range of the CD spectra of (R,R)-1 and (S,S)-1. An irreversible one-electron oxidation wave with an onset potential at 1.07 V is observed by cyclic voltammetry, along with a reversible one-electron reduction wave at -0.85 V. Density functional calculations reproduce the experimentally observed data and trends, and provide further insight into the nature of the electronic transitions.