title: Introducing asymmetry in tetradentate azadipyrromethene chromophores: a systematic study of the impact on electronic and photophysical properties.
abstract: As analogues of the porphyrinoid and dipyrromethene families of dye, azadipyrromethene (ADPM) derivatives exhibit exciting photophysical properties. Their high absorbance (ε up to 100,000 M(-1) cm(-1)) in the yellow-to-red region and the strong NIR luminescence encountered in boron-chelated aza-BODIPY analogues are especially interesting in the context of light-harvesting and life science applications. In the present study, we endeavoured to compare symmetric and asymmetric tetradentate ADPM derivatives 1-6 versus two related bidentate ADPM references in order to gain insights into their structure-property relationship. This is of interest since the tetradentate motif opens the way for extended π-conjugation through metal-mediated planarization, in a bio-mimicry fashion of metalloporphyrinoids, and is known to induce a bathochromic shift toward the NIR. A new straightforward synthetic approach is used to access asymmetric derivatives 4-6 that avoids the tedious heterocycle formation of nitroso-pyrrole intermediates. In addition, photophysics, electrochemistry, computational modelization (DFT and TD-DFT) and X-ray structural characterization of ADPMs are used to better understand the potential of these new chromophores.
authors.affiliation: Département de Chimie, Université de Montréal, Pavillon J.-A. Bombardier, 5155 Decelles Avenue, Montréal, Québec H3T-2B1, Canada. garry.hanan@umontreal.ca.
authors.forename: André
authors.initials: A
authors.lastname: Bessette
authors.forename: Mihaela
authors.initials: M
authors.lastname: Cibian
authors.forename: Francis
authors.initials: F
authors.lastname: Bélanger
authors.forename: Denis
authors.initials: D
authors.lastname: Désilets
authors.forename: Garry S
authors.initials: GS
authors.lastname: Hanan