title: Pyridyl-functionalised 3H-1,2,3,4-triazaphospholes: synthesis, coordination chemistry and photophysical properties of low-coordinate phosphorus compounds.
abstract: Novel conjugated, pyridyl-functionalised triazaphospholes with either tBu or SiMe3 substituents at the 5-position of the N3 PC heterocycle have been prepared by a [3+2] cycloaddition reaction and compared with structurally related, triazole-based systems. Photoexcitation of the 2-pyridyl-substituted triazaphosphole gives rise to a significant fluorescence emission with a quantum yield of up to 12 %. In contrast, the all-nitrogen triazole analogue shows no emission at all. DFT calculations indicate that the 2-pyridyl substituted systems have a more rigid and planar structure than their 3- and 4-pyridyl isomers. Time-dependent (TD) DFT calculations show that only the 2-pyridyl-substituted triazaphosphole exhibits similar planar geometry, with matching conformational arrangements in the lowest energy excited state and the ground state; this helps to explain the enhanced emission intensity. The chelating P,N-hybrid ligand forms a Re(I) complex of the type [(N^N)Re(CO)3 Br] through the coordination of nitrogen atom N(2) to the metal centre rather than through the phosphorus donor. Both structural and spectroscopic data indicate substantial π-accepting character of the triazaphosphole, which is again in contrast to that of the all-nitrogen-containing triazoles. The synthesis and photophysical properties of a new class of phosphorus-containing extended π systems are described.
authors.affiliation: Institut für Chemie und Biochemie, Anorganische Chemie, Freie Universität Berlin, Fabeckstr. 34/36, 14195 Berlin (Germany).
authors.forename: Julian A W
authors.initials: JA
authors.lastname: Sklorz
authors.affiliation: Institut für Chemie und Biochemie, Anorganische Chemie, Freie Universität Berlin, Fabeckstr. 34/36, 14195 Berlin (Germany).
authors.forename: Santina
authors.initials: S
authors.lastname: Hoof
authors.affiliation: Institut für Chemie und Biochemie, Anorganische Chemie, Freie Universität Berlin, Fabeckstr. 34/36, 14195 Berlin (Germany).
authors.forename: Nadine
authors.initials: N
authors.lastname: Rades
authors.affiliation: Institut des Sciences Chimiques de Rennes, UMR 6226 CNRS - Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex (France).
authors.forename: Nicolas
authors.initials: N
authors.lastname: De Rycke
authors.affiliation: Budapest University of Technology and Economics, Department of Inorganic and Analytical Chemistry, Szt. Gellért tér 4, 1521 Budapest (Hungary).
authors.forename: László
authors.initials: L
authors.lastname: Könczöl
authors.affiliation: Budapest University of Technology and Economics, Department of Inorganic and Analytical Chemistry, Szt. Gellért tér 4, 1521 Budapest (Hungary).
authors.forename: Dénes
authors.initials: D
authors.lastname: Szieberth
authors.affiliation: Institut für Chemie und Biochemie, Anorganische Chemie, Freie Universität Berlin, Fabeckstr. 34/36, 14195 Berlin (Germany).
authors.forename: Manuela
authors.initials: M
authors.lastname: Weber
authors.affiliation: Institut für Chemie und Biochemie, Anorganische Chemie, Freie Universität Berlin, Fabeckstr. 34/36, 14195 Berlin (Germany).
authors.forename: Jelena
authors.initials: J
authors.lastname: Wiecko
authors.affiliation: Budapest University of Technology and Economics, Department of Inorganic and Analytical Chemistry, Szt. Gellért tér 4, 1521 Budapest (Hungary). nyulaszi@mail.bme.hu.
authors.forename: László
authors.initials: L
authors.lastname: Nyulászi
authors.affiliation: Institut des Sciences Chimiques de Rennes, UMR 6226 CNRS - Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex (France). muriel.hissler@univ-rennes1.fr.
authors.forename: Muriel
authors.initials: M
authors.lastname: Hissler
authors.affiliation: Institut für Chemie und Biochemie, Anorganische Chemie, Freie Universität Berlin, Fabeckstr. 34/36, 14195 Berlin (Germany). c.mueller@fu-berlin.de.
authors.forename: Christian
authors.initials: C
authors.lastname: Müller
keywords: coordination modes; density functional calculations; heterocycles; luminescence; phosphorus