Optoelectronic Properties of Carbon-Bound Boron Difluoride Hydrazone Dimers

Authors

Daniela Cappello
Ryan R. Maar
Viktor N. Staroverov
Joe GilroyFollow

Document Type

Article

Publication Date

Spring 3-6-2020

Journal

Chemistry - A European Journal

Volume

26

First Page

5522

Abstract

The creation of dimeric boron difluoride complexes of chelating N-donor ligands is a proven strategy for the enhancement of the optoelectronic properties of fluorescent dyes. We report dimers based on the boron difluoride hydrazone (BODIHY) framework, which offer unique and sometimes unexpected substituent-dependent absorption, emission, and electrochemical properties. BODIHY dimers have low-energy absorption bands (l_max = 421 to 479 nm, e = 17,200 to 39,900 M⁻¹ cm⁻¹) that are red-shifted relative to monomeric analogues. THF solutions of these dimers exhibit aggregation-induced emission upon addition of water, with emission enhancement factors ranging from 5 to 18. Thin films of BODIHY dimers are weakly emissive as a result of the inner-filter effect, attributed to intermolecular p-type interactions. BODIHY dimers are redox-active and display two one-electron oxidation and two one-electron reduction waves that strongly depend on the N-aryl substituents. These properties are rationalized using density-functional theory calculations and X-ray crystallography experiments.