Synthesis, Characterization, and Electrochemistry of Copper Dibenzoporphyrin(2.1.2.1) Complexes

Abstract

Three copper dibenzoporphyrin(2.1.2.1) complexes having two dipyrromethene units connected through o-phenylen bridges and 4-MePh, Ph, or F5Ph substituents at the meso positions of the dipyrrins were synthesized and characterized according to their spectral, electrochemical, and structural properties. As indicated by the single-crystal X-ray structures, all three derivatives have highly bent molecular structures, with angles between each planar dipyrrin unit ranging from 89° to 85°, indicative of a nonaromatic molecule. The insertion of copper­(II) into dibenzoporphyrins(2.1.2.1) induced a change in the macrocyclic cavity shape from rectangular in the case of the free-base precursors to approximately square for the metalated copper derivatives. Solution electron paramagnetic resonance (EPR) spectra at 100 K showed hyperfine coupling of the Cu­(II) central metal ion and the N nucleus in the highly bent molecular structures. Electrochemical measurements in CH2Cl2 or N,N-dimethylformamide (DMF) containing 0.1 M tetrabutylammonium perchlorate (TBAP) were consistent with ring-centered electron transfers and, in the case of reduction, were assigned to electron additions involving two equivalent π centers on the bent nonaromatic molecule. The potential separation between the two reversible one-electron reductions ranged from 230 to 400 mV in DMF, indicating a moderate-to-strong interaction between the equivalent redox-active dipyrrin units of the dibenzoporphyrins(2.1.2.1). The experimentally measured highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gaps ranged from 2.14 to 2.04 eV and were smaller than those seen for the planar copper tetraarylporphyrins(1.1.1.1), (Ar)4PCu.

A porphyrin(2.1.2.1) bis-boron complex as a deep-red AIE luminophore induced by intermolecular F–π interaction

“…3. 4 The N–N distances (Fig. 3e) indicate that all four complexes contain rectangular cavities, whereas those of other reported metal complexes are square.…”

“…2 and S11–S15, ESI†). 4 The eight pyrrolic β-protons of 2a and 2b produce four doublet peaks between 6.00 and 6.75 ppm, suggesting the complexes are of lower symmetry than the parent ligands 1a and 1b , which produce two doublet peaks for the pyrrolic β-protons. The fluorine peaks of BF 2 on 2a present at −131 ppm and −151 ppm, supporting the asymmetric structure of 2a (Fig.…”

“…We have developed the synthesis and complexation of porphyrins(2.1.2.1) containing embedded o -phenylenes or dimethylethenes between dipyrrin units. 4 Porphyrins(2.1.2.1) have the powerful ability to form diverse complexes with mono-/di-cationic species, which we sought to exploit in designing new ligands of cyclic boron complexes for which we could investigate a variety of structural and optical properties. In this work, we first report the synthesis of four boron complexes from porphyrins(2.1.2.1) ( 2a , 2b , 3a , and 3b ) containing two types of substituents: phenyl and pentafluorophenyl, at the meso -positions (Scheme 1).…”

“…the condensation of dipyrrolylbenzene ( DPB ) and aromatic aldehydes with a BF 3 ·OEt 2 catalyst (Scheme 1). 4 Characterisation of 1a and 1b was performed by high-resolution matrix-assisted laser desorption/ionization time-of-flight mass (HR-MALDI-TOF-MS) spectrometry, 1 H NMR spectroscopy, and X-ray diffraction analysis (Fig. S2–S6, ESI†).…”

“…The collected data indicates that 1a and 1b form saddle-shaped molecular structures, similar to the reported porphyrins(2.1.2.1). 4 The boron complexes of 1a and 1b were obtained via complexation with BF 3 ·OEt 2 in the presence of triethylamine (TEA), in toluene, and under reflux (Scheme 1). Notably, the mono- and diboron complexes of 1a and 1b were synthesized by a one-pot reaction and could be separated by silica gel chromatography.…”