Structurally Tunable 3‐Cyanoformazanate Boron Difluoride Dyes

Abstract

The straightforward synthesis of a series of 3-cyanoformazanate boron difluoride dyes is reported. Phenyl, 4-methoxyphenyl and 4-cyanophenyl N-substituted derivatives were isolated and characterized by single-crystal X-ray crystallography, cyclic voltammetry, and UV/Vis spectroscopy. The compounds were demonstrated to possess tunable, substituent-dependent absorption, emission, and electrochemical properties, which were rationalized through electronic structure calculations.

Untitled

“…Our current projects include: the synthesis and characterization of stable verdazyl radical polymers for use as hydrophobic hole transport ma terials (Figure 1), 1 the production of highly metallized phos phonium polymers as precursors to novel heterogeneous catalysts, 2 the synthesis and evaluation of π-conjugated me tallopolymers for use in polymer based electronics, 3 and the development of redox active formazanate ligands for use in main group and transition metal coordination chemistry. 4,5 SYNFORM What is your most important scientific achieve ment to date and why?…”

Aggregation-induced emission enhancement in boron difluoride complexes of 3-cyanoformazanates

“…The results were compared to data obtained for 5a (E°r ed1 = −0.68 V, E°r ed2 = −1.82 V) and 5b (E°r ed1 = −0.75 V, E°r ed2 = −1.92 V) and demonstrated that the introduction of ortho methoxy substituents made electrochemical reduction more difficult due to a less planar π system. 16,22 Exploration of the AIEE behaviour of 5a−c in THF-water mixtures with different volume fractions of water (f w ) revealed an interesting trend ( Fig. 1 and Table S1).…”

“…Boron difluoride (BF 2 ) formazanates are an interesting class of molecular materials that possess tunable absorption, emission, and electrochemical properties through structural variation. 16 The parent formazans 4, 17 are commonly used in cell viability assays, 18 and are generally prepared via straightforward aryl diazonium coupling reactions in aqueous media. BF 2 formazanates have been incorporated into polymers, 19 explored as electrochemiluminescent materials, 20 used as precursors to B(I) carbenoid intermediates, 21 and employed as fluorescent cell-imaging agents.…”

“…BF 2 complex 5c was prepared in 96% yield according to a well-established synthetic methodology and the synthesis and characterization of 5a and 5b have been reported elsewhere. 16,22 We chose these methoxy-substituted compounds for this study due to their superior emission properties, specifically, their relatively higher fluorescence quantum yields ( F ) relative to other substituted BF 2 formazanate derivatives. 22 Complex 5c…”

“…The frontier molecular orbitals of 5a have been shown previously to include significant orbital density on these structural features. 16 In addition, there are numerous intermolecular interactions [CHπ (2.763 Å and 2.906 Å), CHO (2.707 Å and 3.060 Å), and CHF (2.478−2.665 Å)], which may enable the formation of excimers (Fig. S8).…”