title: Walking Down the Chalcogenic Group of the Periodic Table: From Singlet to Triplet Organic Emitters.
abstract: The synthesis, X-ray crystal structures, ground- and excited-state UV/Vis absorption spectra, and luminescence properties of chalcogen-doped organic emitters equipped on both extremities with benzoxa-, benzothia-, benzoselena- and benzotellurazole (1X and 2X ) moieties have been reported for the first time. The insertion of the four different chalcogen atoms within the same molecular skeleton enables the investigation of only the chalcogenic effect on the organisation and photophysical properties of the material. Detailed crystal-structure analyses provide evidence of similar packing for 2O -2Se , in which the benzoazoles are engaged in π-π stacking and, for the heavier atoms, in secondary X⋅⋅⋅X and X⋅⋅⋅N bonding interactions. Detailed computational analysis shows that the arrangement is essentially governed by the interplay of van der Waals and secondary bonding interactions. Progressive quenching of the fluorescence and concomitant onset of phosphorescence features with gradually shorter lifetimes are detected as the atomic weight of the chalcogen heteroatom increases, with the tellurium-doped derivatives exhibiting only emission from the lowest triplet excited state. Notably, the phosphorescence spectra of the selenium and tellurium derivatives can be recorded even at room temperature; this is a very rare finding for fully organic emitters.
authors.affiliation: Namur Research College (NARC) and Department of Chemistry, University of Namur (UNamur), Rue de Bruxelles 61, 5000 Namur (Belgium).
authors.forename: Adrian
authors.initials: A
authors.lastname: Kremer
authors.affiliation: Namur Research College (NARC) and Department of Chemistry, University of Namur (UNamur), Rue de Bruxelles 61, 5000 Namur (Belgium).
authors.forename: Claudia
authors.initials: C
authors.lastname: Aurisicchio
authors.affiliation: Namur Research College (NARC) and Department of Chemistry, University of Namur (UNamur), Rue de Bruxelles 61, 5000 Namur (Belgium).
authors.forename: Federica
authors.initials: F
authors.lastname: De Leo
authors.affiliation: Istituto per la Sintesi Organica e la Fotoreattività (ISOF), Consiglio Nazionale delle Ricerche (CNR), Via Gobetti 101, 40129 Bologna (Italy).
authors.forename: Barbara
authors.initials: B
authors.lastname: Ventura
authors.affiliation: Namur Research College (NARC) and Department of Chemistry, University of Namur (UNamur), Rue de Bruxelles 61, 5000 Namur (Belgium).
authors.forename: Johan
authors.initials: J
authors.lastname: Wouters
authors.affiliation: Istituto per la Sintesi Organica e la Fotoreattività (ISOF), Consiglio Nazionale delle Ricerche (CNR), Via Gobetti 101, 40129 Bologna (Italy).
authors.forename: Nicola
authors.initials: N
authors.lastname: Armaroli
authors.affiliation: Istituto per la Sintesi Organica e la Fotoreattività (ISOF), Consiglio Nazionale delle Ricerche (CNR), Via Gobetti 101, 40129 Bologna (Italy). andrea.barbieri@isof.cnr.it.
authors.forename: Andrea
authors.initials: A
authors.lastname: Barbieri
authors.affiliation: Namur Research College (NARC) and Department of Chemistry, University of Namur (UNamur), Rue de Bruxelles 61, 5000 Namur (Belgium). davide.bonifazi@unamur.be.|Department of Chemical and Pharmaceutical Sciences and INSTM UdR Trieste, University of Trieste, Piazzale Europa 1, 34127 Trieste (Italy). davide.bonifazi@unamur.be.
authors.forename: Davide
authors.initials: D
authors.lastname: Bonifazi
keywords: chalcogens; heterocycles; luminescence; photophysics; supramolecular chemistry