Synthesis and properties of the heterospin (S1 = S2 = 1/2) radical-ion salt bis(mesitylene)molybdenum(I) [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazolidyl

The authors are grateful to the Presidium of the Russian Academy of Sciences (Project 8.14), the Royal Society (RS International Joint Project 2010/R3), the Leverhulme Trust (Project IN-2012-094), the Siberian Branch of the Russian Academy of Sciences (Project 13), the Ministry of Education and Science of the Russian Federation (Project of Joint Laboratories of Siberian Branch of the Russian Academy of Sciences and National Research Universities), and the Russian Foundation for Basic Research (Projects 13-03-00072 and 15-03-03242) for financial support of various parts of this work. N.A.S. thanks the Council for Grants of the President of Russian Federation for postdoctoral scholarship (grant MK-4411.2015.3). B.E.B. is grateful for an EaStCHEM Hirst Academic Fellowship. A.V.Z. thanks the Foundation named after D. I. Mendeleev, Tomsk State University, for support of his work.Low-temperature interaction of [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (1) with MoMes2 (Mes = mesitylene / 1,3,5-trimethylbenzene) in tetrahydrofuran gave the heterospin (S1 = S2 = 1/2) radical-ion salt [MoMes2]+[1]– (2) whose structure was confirmed by single-crystal X-ray diffraction (XRD). The structure revealed alternating layers of the cations and anions with the Mes ligands perpendicular, and the anions tilted by 45°, to the layer plane. At 300 K the effective magnetic moment of 2 is equal to 2.40 μB (theoretically expected 2.45 μB) and monotonically decreases with lowering of the temperature. In the temperature range 2−300 K, the molar magnetic susceptibility of 2 is well-described by the Curie-Weiss law with parameters C and θ equal to 0.78 cm3⋅K⋅mol–1 and −31.2 K, respectively. Overall, the magnetic behavior of 2 is similar to that of [CrTol2]+[1]– and [CrCp*2]+[1]–, i.e. changing the cation [MAr2]+ 3d atom M = Cr (Z = 24) with weak spin-orbit coupling (SOC) to a 4d atom M = Mo (Z = 42) with stronger SOC does not affect macroscopic magnetic properties of the salts. For the XRD structure of salt 2, parameters of the Heisenberg spin-Hamiltonian were calculated using the broken-symmetry DFT and CASSCF approaches, and the complex 3D magnetic structure with both the ferromagnetic (FM) and antiferromagnetic (AF) exchange interactions was revealed with the latter as dominating. Salt 2 is thermally unstable and slowly loses the Mes ligands upon storage at ambient temperature. Under the same reaction conditions, interaction of 1 with MoTol2 (Tol = toluene) proceeded with partial loss of the Tol ligands to afford diamagnetic product.PostprintPostprintPeer reviewe

Novel long-lived π-heterocyclic radical anion:a hybrid of 1,2,5-thiadiazo- and 1,2,3-dithiazolidyls

A long-lived π-heterocyclic radical anion of the hybrid 1,2,5-thiadiazolidyl / 1,2,3-dithiazolidyl type was electrochemically generated and characterized by EPR spectroscopy and DFT calculations

Novel long-lived π-heterocyclic radical anion:a hybrid of 1,2,5-thiadiazo- and 1,2,3-dithiazolidyls

A long-lived π-heterocyclic radical anion of the hybrid 1,2,5-thiadiazolidyl / 1,2,3-dithiazolidyl type was electrochemically generated and characterized by EPR spectroscopy and DFT calculations

Electrochemical properties and radical anions of carbocycle-fluorinated quinoxalines and their substituted derivatives

Electrochemical reduction (ECR) and oxidation (ECO) of 5,6,7,8‐tetrafluoroquinoxaline (1) and its derivatives bearing various substituents R (7‐H (2), 7,8‐H2 (3), 6‐CF3 (4), 6‐Cl (5), 5,7‐Cl2 (6), 5‐NH2 (7), 6‐OCH3 (8), 6,7‐(OCH3)2 (9), 6,7,8‐(OCH3)3 (10), 5,6,7,8‐(OCH3)4 (11), 6‐OCH3,7‐N(CH3)2 (12), 6‐N(CH3)2 (13), 6,7‐(N(CH3)2)2 (14), 5,6,7‐(N(CH3)2)3 (15), and 7,8‐cyclo‐(=CF‐CF = CF‐CF=) (16)) in the carbocycle have been studied by cyclic voltammetry in MeCN. For 1–4 and 7–15, the first reduction peaks have been found to be 1‐electron and reversible, thus corresponding to the formation of their radical anions (RAs), which are long lived at 295 K except those of 4–6 and 15, 16. Irreversible hydrodechlorination has been observed for 5 and 6 at the first step of their ECR confirmed by EPR detection of corresponding RAs of 2 and 5,7‐H2 derivative of 1 (17) at the next steps. Electrochemically generated RAs of 1–3, 7–14, and 17 have been characterized in MeCN by EPR spectroscopy together with DFT calculations at the (U)B3LYP/6‐31 + G(d) level of theory using PCM to describe the solvent. A noticeable alternation of spin density on the –NCCN– moiety of quinoxaline has been observed for all RAs possessing R‐substitution asymmetry. The comparative electron‐accepting ability of 1–15 has been analyzed in terms of their experimental reduction peak potentials and the (U)B3LYP/6‐31 + G(d)‐calculated gas‐phase first adiabatic electron affinities (EAs). The differences in electron transfer solvation energies for 1–15 have been evaluated on the basis of ECR peaks' potentials and calculated gas‐phase EAs. The ECO of 1–5 and 7–14 has been found to be irreversible

Electrochemical properties and radical anions of carbocycle-fluorinated quinoxalines and their substituted derivatives

Electrochemical reduction (ECR) and oxidation (ECO) of 5,6,7,8‐tetrafluoroquinoxaline (1) and its derivatives bearing various substituents R (7‐H (2), 7,8‐H2 (3), 6‐CF3 (4), 6‐Cl (5), 5,7‐Cl2 (6), 5‐NH2 (7), 6‐OCH3 (8), 6,7‐(OCH3)2 (9), 6,7,8‐(OCH3)3 (10), 5,6,7,8‐(OCH3)4 (11), 6‐OCH3,7‐N(CH3)2 (12), 6‐N(CH3)2 (13), 6,7‐(N(CH3)2)2 (14), 5,6,7‐(N(CH3)2)3 (15), and 7,8‐cyclo‐(=CF‐CF = CF‐CF=) (16)) in the carbocycle have been studied by cyclic voltammetry in MeCN. For 1–4 and 7–15, the first reduction peaks have been found to be 1‐electron and reversible, thus corresponding to the formation of their radical anions (RAs), which are long lived at 295 K except those of 4–6 and 15, 16. Irreversible hydrodechlorination has been observed for 5 and 6 at the first step of their ECR confirmed by EPR detection of corresponding RAs of 2 and 5,7‐H2 derivative of 1 (17) at the next steps. Electrochemically generated RAs of 1–3, 7–14, and 17 have been characterized in MeCN by EPR spectroscopy together with DFT calculations at the (U)B3LYP/6‐31 + G(d) level of theory using PCM to describe the solvent. A noticeable alternation of spin density on the –NCCN– moiety of quinoxaline has been observed for all RAs possessing R‐substitution asymmetry. The comparative electron‐accepting ability of 1–15 has been analyzed in terms of their experimental reduction peak potentials and the (U)B3LYP/6‐31 + G(d)‐calculated gas‐phase first adiabatic electron affinities (EAs). The differences in electron transfer solvation energies for 1–15 have been evaluated on the basis of ECR peaks' potentials and calculated gas‐phase EAs. The ECO of 1–5 and 7–14 has been found to be irreversible