title: Strongly Phosphorescent Transition Metal π-Complexes of Boron-Boron Triple Bonds.
abstract: Herein are reported the first π-complexes of compounds with boron-boron triple bonds with transition metals, in this case CuI. Three different compounds were isolated that differ in the number of copper atoms bound to the BB unit. Metalation of the B-B triple bonds causes lengthening of the B-B and B-CNHCbonds, as well as large upfield shifts of the11B NMR signals, suggesting greater orbital interactions between the boron and transition metal atoms than those observed with recently published diboryne/alkali metal cation complexes. In contrast to previously reported fluorescent copper(I) π-complexes of boron-boron double bonds, the Cun-π-diboryne compounds (n = 2, 3) show intense phosphorescence in the red to near-IR region from their triplet excited states, according to their microsecond lifetimes, with quantum yields of up to 58%. While the Cu diborene bond is dominated by electrostatic interactions, giving rise to S1and T1states of pure IL(π-π*) nature, DFT studies show that the CuIπ-complexes of diborynes reported herein exhibit enhanced metal d orbital contributions to HOMO and HOMO-1, which results in S1and T1having significant MLCT character, enabling strong spin-orbit coupling for highly efficient intersystem-crossing S1→ Tnand phosphorescence T1→ S0.
authors.affiliation: Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg , Am Hubland, 97074 Würzburg, Germany.|Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg , Am Hubland, 97074 Würzburg, Germany.
authors.forename: Holger
authors.identifier: 0000-0001-9264-1726
authors.initials: H
authors.lastname: Braunschweig
authors.affiliation: Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg , Am Hubland, 97074 Würzburg, Germany.|Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg , Am Hubland, 97074 Würzburg, Germany.
authors.forename: Theresa
authors.initials: T
authors.lastname: Dellermann
authors.affiliation: Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg , Am Hubland, 97074 Würzburg, Germany.|Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg , Am Hubland, 97074 Würzburg, Germany.
authors.forename: Rian D
authors.initials: RD
authors.lastname: Dewhurst
authors.affiliation: Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg , Am Hubland, 97074 Würzburg, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Hupp
authors.affiliation: Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg , Am Hubland, 97074 Würzburg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Kramer
authors.affiliation: Department of Chemistry, School of Life Sciences, University of Sussex , Brighton BN1 9QJ, Sussex, United Kingdom.
authors.forename: James D
authors.initials: JD
authors.lastname: Mattock
authors.affiliation: Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg , Am Hubland, 97074 Würzburg, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Mies
authors.affiliation: Department of Chemical Sciences, Tezpur University Napaam , 784028 Assam, India.
authors.forename: Ashwini K
authors.initials: AK
authors.lastname: Phukan
authors.affiliation: Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg , Am Hubland, 97074 Würzburg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Steffen
authors.affiliation: Department of Chemistry, School of Life Sciences, University of Sussex , Brighton BN1 9QJ, Sussex, United Kingdom.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Vargas