Taisiya S. Sukhikh

Novel applications of functionalized 2,1,3- benzothiadiazoles for coordination chemistry and crystal engineering†

Two novel applications of functionalized 2,1,3-benzothiadiazoles for metal coordination chemistry and crystal engineering of organic solids are presented. 4-Amino-2,1,3-benzothiadiazole (1) forms a 2 : 1 complex with ZnCl2 (complex 2) and a 1 : 1 complex with 4-nitro-2,1,3-benzothiadiazole (3) (complex 4). The structures of compounds 1–4 were confirmed by single-crystal X-ray diffraction and studied by UV-Vis and IR spectroscopy, and DFT and QTAIM calculations. Complex 2 is the first structurally defined Zn complex with 2,1,3-benzothiadiazole ligands. In this complex, both molecules 1 are coordinated to Zn only by amino groups, thus revealing a novel type of coordination of this ligand to the metal center. According to 1H NMR data, complex 2 dissociates in CHCl3, THF or DMSO solutions. There are only a few examples of similar complexes, which are also considered to dissociate in solutions. In crystalline complex 4, molecules 1 and 3 form infinite alternating π-stacks connected by lateral S⋯N interactions between the neighboring stacks. Intermolecular S⋯N interactions are also observed in the crystals of individual 1 and 3 but the packing motifs are different from those in 4. DFT calculations predict a small charge transfer (CT, ∼0.02e at B97-D3 level) from 1 to 3 upon the formation of 4, which therefore is an unprecedented CT complex where both donor and acceptor moieties are the derivatives of the 2,1,3-benzothiadiazole ring system. This finding creates some new prospects for the crystal engineering of organic solids. Crystalline complex 4 is characterized by an intense CT absorption band with a maximum at ∼550 nm. However, according to DFT and QTAIM calculations the complex is weakly bonded and its formation is not observed in CH2Cl2 solution with 1H NMR and UV-Vis techniques.

Novel luminescent β-ketoimine derivative of 2,1,3-benzothiadiazole: synthesis, complexation with Zn(II) and photophysical properties in comparison with related compounds

A novel β-ketoimine-functionalized 2,1,3-benzothiadiazole (4-(2,1,3-benzothiadiazole-4-ylamino)pent-3-en-2-one, L2H) was synthesized and used as chelating ligand for the complexation with Zn(II) (complex ZnL2). The spectroscopic and photophysical properties of L2H and ZnL2 as well as those of previously described 4-amino-2,1,3-benzothiadiazole (L1) and its complex ZnL1 have been thoroughly studied in the crystalline state and solution. The UV-Vis absorption spectra of free ligands L1, L2H and its deprotonated form L2−, and complexes ZnL1 and ZnL2 were assigned on the basis of TD-DFT calculations. In contrast to ZnL2 having conventional single-band fluorescence, ZnL1 demonstrates a broad double-band purple-white fluorescence spanning the entire visible region. On the basis of careful spectroscopic studies the second band of this unusual fluorescence spectrum was attributed to the presence of traces of free ligand L1 in the crystals of complex ZnL1. The energy transfer from the excited state of ZnL1 to a free ligand L1 was revealed.

New red-luminescent cadmium coordination polymers with 4-amino-2,1,3-benzothiadiazole

Abstract New polymeric cadmium complexes, α-[CdLCl2]n (1), [CdL2Cl2]n (2) and β-[CdLCl2]n (3) (L = 4-amino-2,1,3-benzothiadiazole), were obtained as products of the reaction of CdCl2 with L. The synthetic procedures allowing isolation of pure 1–3 were optimized. The structures of 1–3 were established by single-crystal X-ray diffraction and the compounds were characterized by UV–Vis and IR spectroscopy. In these compounds, L is either μ-bridging (1) or terminal (2 and 3). The UV–Vis spectra of the complexes in the solid state resemble that of free L. However, coordination of L leads to a significant shift of emission in photoluminescence spectra from yellow (free L) to red (1–3).

Crystal structures of [Ln5(dbm)10(OH)5]·nCH2Cl2 (Ln = Yb, n = 2, Ln = Er, n = 6)

The structures of [Yb5(dbm)10(OH)5]·2CH2Cl2 and [Er5(dbm)10(OH)5]·6CH2Cl2 (dbm = dibenzoylmethanate) were established. The compounds are crystallized in different space groups P4/n and P21/n correspondingly. Ytterbium complex is isostructural to known [Ln5(dbm)10(OH)5]·2C7H8 (Ln = Er, Yb). Structural type of erbium complex prepared in this work has no analogues amongst similar pentanuclear dibenzoylmethanate complexes. The cavities types of the structures filled by CH2Cl2 molecules are different.

Crystal structure and properties of (1,5-cyclooctadiene) (η 5 -pentamethylcyclopentadienyl) iridium(I) [Ir(cod)Cp*]

Volatile iridium(I) complexes [Ir(cod)Cpx] (Cpx = pentamethylcyclopentadienyl Cp*, ethylcyclopentadienyl CpEt, cod = 1,5-cyclooctadiene) are synthesized and characterized by IR and NMR spectroscopy. The [Ir(cod)Cp*] complex is a solid and the [Ir(cod)CpEt] complex is a liquid (SATP). The XRD method is used to determine the structure of the [Ir(cod)Cp*] complex: chemical formula C18H27Ir, space group P21/c, a = 8,4418(2) Å, b = 9,4764(3) Å, c = 19.2682(5) Å, β = 96.128(1) °, V = 1532.61(7) Å3, Z = 4, dcalc = 1.888 g/cm3, μ = 8.697 mm–1. The cyclopentadienyl ligand is η5-type coordinated; 1,5-cyclooctadiene have a cis-cis conformation and is η4-type coordinated. The thermal properties of the complexes are studied by thermogravimetry.

Crystal Structure of Binuclear Cobalt Complexes [(Cp′′′Co)2(μ2-η1:η2-S2)2] and [(Cp′′′Co)2(μ2-η1:η2-Se2)2]

Binuclear cobalt complexes [(Cp′′′Co)2(μ2-η1:η2-S2)2] (1) (Cp′′′ = η5-1,2,4-tris(tert-butyl)cyclopentadienide) and [(Cp′′′Co)2(μ2-η1:η2-Se2)2] (2) are obtained by the interaction of [(Cp′′′Co)2(μ-η4:η4-C7H8)] with excess sulfur or selenium respectively. The structures of the complexes are determined by single crystal X-ray diffraction.

Crystal structure of a Zn complex with tereph­thalate and 1,6-bis­(1,2,4-triazol-1-yl)hexa­ne

A new Zn coordination polymer with bitopic rigid terephthalate and flexible 1,6-bis(1,2,4-triazol-1-yl)hexane was synthesized and structurally characterized.