Hui-Fang Wang

Multi-dimensional iodocuprates of 4-cyanopyridinium and N,N′-dialkyl-4,4′-bipyridinium: syntheses, structures and dielectric properties

Solvothermal reactions of CuI with 4-cyanopyridine (4-cypy) or 4,4′-bipyridine (4,4′-bipy) and alcohols (methanol, ethanol, propanol, isopropanol) in the presence of I2 and a trace amount of water in acetonitrile gave rise to a family of multi-dimensional iodocuprate complexes of 4-cyanopyridinium and N,N′-dialkyl-4,4′-bipyridinium including {[MC]2[Cu4(μ3-I)4(μ-I)2]}n (MC+ = N-methyl-4-cyanopyridium) (1), {[PC][(Cu2I4)1/4(Cu2I4)1/4]}n (PC+ = N-propyl-4-cyanopyridinium) (2), {[iPC][(Cu2I4)1/4((Cu1/2)4I4)1/4]}n (iPC+ = N-isopropyl-4-cyanopyridium) (3), {[EV]1/4[((Cu1/2)4I4)1/4]}n (EV2+ = N,N′-diethyl-4,4′-bipyridinium) (4) and {[PV]1/2[(Cu2I4)1/4((Cu1/2)4I4)1/4]}n (PV2+ = N,N′-dipropyl-4,4′-bipyridinium) (5). The resulting 4-cyanopyridinium and viologen cations were generated in situ via the cleavage of the C–O bond of alcohols followed by alkylation of 4-cypy or 4,4′-bipy. X-ray analysis revealed that compound 1 consists of a unique three-dimensional anionic [Cu4I6]n2n− framework while compounds 2–5 contain one-dimensional anionic [Cu2I4]n2n− chains that are enclosed into different cationic channels formed by either 4-cyanopyridinium or N,N′-dialkyl-4,4′-bipyridinium. The dielectric properties of 1–5 were investigated.

A Mn(iii)–superoxo complex of a zwitterionic calix[4]arene with an unprecedented linear end-on Mn(iii)–O2 arrangement and good catalytic performance for alkene epoxidation

Reactions of [H(4)L][PF(6)](4) with 4 equiv. of Mn(OAc)(2)·4H(2)O in the presence of air gave rise to a mononuclear Mn(III)-superoxo complex [Mn(III)L(O(2))(H(2)O)](PF(6))(2), which contains a bowl-shaped cationic structure with a D(4d) symmetry. It has an unprecedented linear end-on Mn(III)-O(2) unit and exhibited good efficiency and selectivity in the catalytic oxidation of alkenes with O(2) plus isobutyraldehyde under mild conditions.

Construction of halide-bridged tungsten-copper-sulfide double cubanelike clusters from a new precursor [(Tp*WS2)2(μ-S2)].

Treatment of [Et(4)N][Tp*WS(3)] (1) (Tp* = hydridotris(3,5-dimethylpyrazol-1-yl)borate) with 2 equiv of AgSCN in MeCN afforded a novel neutral compound [(Tp*WS(2))(2)(μ-S(2))] (2). Reactions of 2 with excess CuX (X = Cl, Br, I) in MeCN and CH(2)Cl(2) or CHCl(3) formed three neutral W/Cu/S clusters [{Tp*W(μ(3)-S)(3)Cu(3)(μ-Cl)}(2)Cu(μ-Cl)(2)(μ(7)-Cl)(MeCN)](2) (3), [{Tp*W(μ(3)-S)(3)Cu(3)}(2)Br(μ-Br)(2)(μ(4)-Br)(MeCN)] (4), and [{Tp*W(μ(3)-S)(3)Cu(3)}(2){Cu(2)(μ-I)(4)(μ(3)-I)(2)}] (5), respectively. On the other hand, treatment of 2 with CuX (X = Cl, Br) in the presence of Et(4)NX (X = Cl, Br) produced two anionic W/Cu/S clusters [Et(4)N][{Tp*W(μ(3)-S)(3)Cu(3)X}(2)(μ-X)(2)(μ(4)-X)] (6: X = Cl; 7 X = Br). Compounds 2-7 were characterized by elemental analysis, IR, UV-vis, (1)H NMR, electrospray ionization (ESI) mass spectra, and single-crystal X-ray crystallography. The dimeric structure of 2 can be viewed as two [Tp*WS(2)] fragments in which two W atoms are connected by one S(2)(2-) dianion. Compounds 3-7 all possess unique halide-bridged double cubanelike frameworks. For 3, two [Tp*W(μ(3)-S)(3)Cu(3)](2+) dications are linked via a μ(7)-Cl(-) bridge, two μ-Cl(-) bridges, and a [Cu(MeCN)(μ-Cl)(2)](+) bridge. For 4, one [Tp*W(μ(3)-S)(3)Cu(3)(MeCN)](2+) dication and one [Tp*W(μ(3)-S)(3)Cu(3)Br](+) cation are linked via a μ(4)-Br(-) and two μ-Br(-) bridges. For 5, the two [Tp*W(μ(3)-S)(3)Cu(3)](2+) dications are bridged by a linear [(μ-I)(2)Cu(μ(3)-I)(2)Cu(μ-I)(2)](4+) species. For 6 and 7, two [Tp*W(μ(3)-S)(3)Cu(3)X](+) cations are linked by a μ(4)-X(-) and two μ-X(-) bridges (X = Cl, Br). In addition, the third-order nonlinear optical (NLO) properties of 2-7 in MeCN/CH(2)Cl(2) were investigated by using femtosecond degenerate four-wave mixing (DFWM) technique.

Theoretical view on a linear end-on manganese–dioxygen complex bearing a calix[4]arene ligand

By taking a Mn–dioxygen complex supported by a zwitterionic calix[4]arene ligand ([MnL(O2)(H2O)](PF6)2; H4L = [5,11,17,23-tetrakis(trimethylammonium)-25,26,27,28-tetrahydroxycalix[4]arene], CSD refcode: CAGVAJ) as a model system, we investigated the geometric and electronic structures of [MnL(O2)(H2O)]2+ through density functional theory (DFT) calculations without and with the presence of additional waters. It was found that the ground-state structure of [MnL(O2)(H2O)]2+ possesses a typical bent end-on binding mode (Mn–O–O angle at around 130° and dioxygen bond length at ∼1.32 A) within a sextet state (S = 5/2) irrespective of calculated methodologies. The experimently proposed linear end-on structure (Mn–O–O angle at ∼180°) and the side-on structure (Mn–O–O angle ∼75°) are shown to be transition-state structures in the process of dioxygen flipping from one bent-end-on structure to another. By the inclusion of water solvation effect via both the explicit water-cluster model ([MnL(O2)(H2O)]2+–nH2O, n = 1, 4, 6, 8) and implicit CPCM solvation model, a good correlation was concluded: the more additional waters and the more contracted Oe square benefit the larger Mn–O–O angle, indicating a water solvation effect and a ligand size effect. Inspired by the relationship of linear end-on mode with bent end-on mode and the consistence of the projected dioxygen bond length of [MnL(O2)(H2O)]2+–8H2O in the CPCM model along the Mn–O bond direction (dO1–O2(p) = 1.240 A) with the experimental dioxygen bond length (1.249 A), we concluded that the linear Mn–O–O arrangement fitted by experimentalists should be a result of the flipping motion of dioxygen rotating about the Mn–O bond in solid-state structures of the [MnL(O2)(H2O)](PF6)2 complex based on analyses of the crystallographic data. Natural bond orbital (NBO) analyses show the sextet [MnL(O2)(H2O)]2+–nH2O (n = 0, 1, 4, 6, 8) have a Mn(III)-superoxo nature, consistent with experimental observations. The differences in the bonding structures of the three binding modes were discussed by the second-order perturbation energies ΔEi→j from the superoxo lone pair (LP) orbitals to Mn(III) 3d orbitals in β electron space. It can also give clues about the instability of the linear end-on binding mode and the increased Mn–O–O angle in the presence of water solvents.

CCDC 800045: Experimental Crystal Structure Determination

Related Article: Ai-Xia Zheng, Zhi-Gang Ren, Hui-Fang Wang, Hong-Xi Li, Jian-Ping Lang|2012|Inorg.Chim.Acta|382|43|doi:10.1016/j.ica.2011.10.008