title: New Charge-Transfer Complexes with 1,2,5-Thiadiazoles as Both Electron Acceptors and Donors Featuring an Unprecedented Addition Reaction.
abstract: The design and synthesis of novel charge-transfer (CT) complexes are of interest for fundamental chemistry and applications to materials science. In addition to the recently described first CT complex with both electron acceptor (A) and donor (D) groups belonging to the 1,2,5-thiadiazole series (1; A: 4-nitro-2,1,3-benzothiadiazole; D: 4-amino-2,1,3-benzothiadiazole), herein novel CT complexes 2 and 3 with 1,2,5-thiadiazoles as both A (4,6-dinitro-2,1,3-benzothiadiazole and [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole) and D (4-amino-2,1,3-benzothiadiazole) were synthesized. The series is completed by complex 4 with [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole as A and phenoxatellurine as D. Structures of complexes 2-4 were characterized by single-crystal X-ray diffraction (XRD), as well as solution and solid-state UV/Vis spectroscopy. Thermodynamics of their formation were obtained by density functional theory (DFT) calculations, their bonding situations were analyzed by quantum theory of atoms in molecules (QTAIM) calculations and dimer model energies of interactions quantified in the framework of the Hirshfeld surface (HS) analysis. With DFT calculations, the largest value of CT between D and A was found for complex 2, with 0.027 e in the XRD structure and 0.150 e in the optimized structure in MeCN. In the UV/Vis spectra, the λmaxof the CT bands of 2-4 varied in the range λ=517-705 nm. Model energy calculations for 1-4 revealed the importance of both dispersion interactions and hydrogen bonding between D and A as contributors to CT in the crystalline state. In an attempt to enlarge the CT value with bis[1,2,5-thiadiazolo][3,4-b;3',4'-e]pyrazine as A and 4-amino-2,1,3-benzoselenadiazole as D, an unprecedented 1:1 addition reaction was observed upon formation of a C-N bond between atom C7 of D and pyrazine atom N4 of A, accompanied by hydrogen atom transfer from C7 to another pyrazine atom N8 (compound 5). According to DFT calculations, the reaction is a multistep process featuring diradical intermediates and hydrogen atom intramolecular migration over four positions. Molecular and crystal structures of 5 (solvate with toluene) were elucidated by XRD and the crystal structure revealed a rather unusual porous framework.
authors.affiliation: Department of Natural Sciences, Novosibirsk State University, 630090, Novosibirsk, Russia.|Institute of Organic Chemistry, Russian Academy of Sciences, 630090, Novosibirsk, Russia.|Institute of Chemical Kinetics and Combustion, Russian Academy of Sciences, 630090, Novosibirsk, Russia.
authors.forename: Elena A
authors.initials: EA
authors.lastname: Chulanova
authors.affiliation: Department of Natural Sciences, Novosibirsk State University, 630090, Novosibirsk, Russia.
authors.forename: Elena A
authors.initials: EA
authors.lastname: Pritchina
authors.affiliation: Institute for Inorganic Chemistry and Crystallography, University of Bremen, 28359, Bremen, Germany.
authors.forename: Lorraine A
authors.initials: LA
authors.lastname: Malaspina
authors.affiliation: Institute for Inorganic Chemistry and Crystallography, University of Bremen, 28359, Bremen, Germany.
authors.forename: Simon
authors.initials: S
authors.lastname: Grabowsky
authors.affiliation: Institute for Inorganic Chemistry and Crystallography, University of Bremen, 28359, Bremen, Germany.
authors.forename: Farzin
authors.initials: F
authors.lastname: Mostaghimi
authors.affiliation: Institute for Inorganic Chemistry and Crystallography, University of Bremen, 28359, Bremen, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Beckmann
authors.affiliation: Department of Natural Sciences, Novosibirsk State University, 630090, Novosibirsk, Russia.|Institute of Organic Chemistry, Russian Academy of Sciences, 630090, Novosibirsk, Russia.
authors.forename: Irina Yu
authors.initials: IY
authors.lastname: Bagryanskaya
authors.affiliation: Department of Physics, Novosibirsk State University, 630090, Novosibirsk, Russia.
authors.forename: Margarita V
authors.initials: MV
authors.lastname: Shakhova
authors.affiliation: Institute of Organic Chemistry, Russian Academy of Sciences, 119991, Moscow, Russia.|Education and Research Center for Nanotechnology, South Ural State University, 454080, Chelyabinsk, Russia.
authors.forename: Lidia S
authors.initials: LS
authors.lastname: Konstantinova
authors.affiliation: Institute of Organic Chemistry, Russian Academy of Sciences, 119991, Moscow, Russia.|Education and Research Center for Nanotechnology, South Ural State University, 454080, Chelyabinsk, Russia.
authors.forename: Oleg A
authors.initials: OA
authors.lastname: Rakitin
authors.affiliation: Institute of Chemical Kinetics and Combustion, Russian Academy of Sciences, 630090, Novosibirsk, Russia.|Department of Physics, Novosibirsk State University, 630090, Novosibirsk, Russia.
authors.forename: Nina P
authors.initials: NP
authors.lastname: Gritsan
authors.affiliation: Institute of Organic Chemistry, Russian Academy of Sciences, 630090, Novosibirsk, Russia.|Department of Physics, Novosibirsk State University, 630090, Novosibirsk, Russia.
authors.forename: Andrey V
authors.initials: AV
authors.lastname: Zibarev
keywords: X-ray diffraction; chalcogens; charge transfer; donor-acceptor systems; quantum chemistry