Boron calixphyrin complexes: exploring the coordination chemistry of a BODIPY/porphyrin hybrid

Abstract

Boron complexes of calix[4]phyrins (1.1.1.1) were prepared by reacting the free-base ligands with BF·EtO. The reaction conditions can be efficiently tailored to produce mono- or di-boron calixphyrins. Mono-BF calixphyrins with boron coordinating to either the dipyrrin, BF[H(Calix)], or dipyrromethane, BF[H(Calix)] and BF[H(Calix)], bonding sites were isolated. The dipyrromethane isomer, BF[H(Calix)], isomerises into BF[H(Calix)] which kinetic studies and DFT calculations indicate is an intramolecular process. Two isomers of BOF(Calix) were isolated, one isomer bonding via the dipyrrin sites with the FBOBF moiety in cisoid geometry, and the second isomer bonding via the dipyrromethane sites with the FBOBF moiety in transoid geometry. Although the cisoid/dipyrrin isomer was calculated to be most energetically favourable for BOF(Calix), the isolation of the transoid/dipyrromethane isomer is postulated to occur via the presumed intermediate (BF)(Calix), for which DFT indicated a preference for transoid/dipyrromethane geometry.

Rectangular Holes in Porphyrin Isomers Act As Mono- and Binucleating Ligands: Stereochemistry of Mono- and Diboron Porphycenes and Their Protonation Behaviors

“…Both cisoid and transoid examples of B 2 OF 2 complexes of calixphyrins have been reported. 9 Recently, boron complexes of phthalocyanine (transoid-B 2 OF 2 ) and porphyrazine (cisoid-B 2 OF 2 ) were reported by Brothers and co-workers. 10 On the basis of the experiment data and a DFT study, they further elucidated the factor influencing the cisoid/ transoid preference of diboron tetrapyrrole macrocycle complexes, which should be correlated to the ease with which the macrocycles accommodated a rectangularly distorted N 4 cavity.…”

Doubly N‐Confused Calix[6]phyrin Bis‐Organopalladium Complexes: Photostable Triplet Sensitizers for Singlet Oxygen Generation

“…Calixphyrin is aunique class of the porphyrin analogues containing one or multiple sp 3 -hybridized meso-carbon bridges providing intrinsicm olecular flexibility to endure facile cation bindings. [11] From the interest of the effect of the carbon-metal bond in the macrocyclic core forp hotosensitizers, we have been workingo nt he modified( confused) carbaporphyrinoid and calix[4]phyrin(1.1.1.1)m etal complexes. [12,13] Despite the disrupted p-conjugation in the parent tetrapyrrolic scaffold, the NIR light absorption was achieved by electronicp erturbation through an N-confusion modification of the platinum calix[4]phyrin complexes ( Figure 1).…”

Effect of methyl at the 1-phenyl of tetraaryl substituted imidazole boron difluoride complexes: synthesis, characterization, photophysical and electrochemical studies

“…The B-O and B-N bond lengths are amenable to those other literature reported boron complexes. 7,10,32,33 N,O Chelation favors the six-membered boron ring with a twisted conformation. In such a twist the coplanarity is lost between the imidazole and phenolate rings.…”

“…Tetra-coordinated boron compounds as emissive dyes have gained research interest due to their potential applications in sensing, imaging, and organic light emitting diodes. [1][2][3][4][5][6][7][8][9][10][11][12][13] Much effort has been devoted to the development of N,N-coordinated boron dipyrromethene (BODIPY) derivatives because of their excellent photophysical properties and diverse chemistry. 14,15 However, very poor solid-state emission and small Stokes shift and low photostability limit its potential applications.…”