Collisional de-excitation of the metastableD-states of Ba+ by He,Ne, N2 and H2

The rate constants 〈σ · υ〉 for collisional de-excitation of the metastable 5D states of Ba⁺ ions have been determined in an ion trap experiment. TheD-states are selectively populated by pulsed laser excitation of the 6P _1/2 or 6P _3/2 state and the decay at different background pressures is monitored by the change in fluorescence intensity of the excited ions. From the pressure dependence of the decay constants we calculate the de-excitation rate constants for different collision partners, averaged over the velocity distribution of the trapped ion cloud. For He, Ne, H₂ and N₂ we obtain in the c.m. energy range of 0.1–0.5 eV: 〈σ·υ〉 (He)=3.0±0.2·10^?13cm³/s, 〈σ·υ〉 (Ne)=5.1±0.4·10^?13cm³/s, 〈σ·υ〉 (H₂)=3.7±0.3·10^?11cm³/s, 〈σ·υ〉 (N₂)=4.4±0.3·10^?11cm³/s. The results can be understood qualitatively by a consideration of the ion-atom and ion-molecules interaction potential.     

Dynamics of thin polymer films: Recent insights from incoherent neutron scattering

Incoherent neutron scattering is presented as a powerful tool for interpreting changes in molecular dynamics as a function of film thickness for a range of polymers. Motions on approximately nanosecond and faster timescales are quantified in terms of a mean-square atomic displacement (〈u²〉) from the Debye–Waller factor. Thin-film confinement generally leads to a reduction of 〈u²〉 in comparison with the bulk material, and this effect becomes especially pronounced when the film thickness approaches the unperturbed dimensions of the macromolecule. Generally, there is a suppression (never an enhancement) of 〈u²〉 at temperatures T above the bulk calorimetric glass-transition temperature (T_g). Below T_g, the reduction in the magnitude of 〈u²〉 depends on the polymer and the length scales being probed. Polymers with extensive segmental or local mobility in the glass are particularly susceptible to reductions of 〈u²〉 with confinement, especially at the Q vectors probing these longer length scales, whereas materials lacking these sub-T_g motions are relatively insensitive. Moreover, a reduced 〈u²〉 value correlates with reduced mobility at long time and spatial scales, as measured by diffusion in these thin polymer films. Finally, this reduced thin-film mobility is not reliably predicted by thermodynamic assessments of an apparent T_g, as measured by discontinuities or kinks in the T dependence of the thermal expansion, specific volume, index of refraction, specific heat, and so forth. These measurements illustrate that 〈u²〉 is a powerful and predictive tool for understanding dynamic changes in thin polymer films. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3218–3234, 2004     

The oblique chiral nematic phase in calamitic bimesogens

ABSTRACT

The discovery of the oblique chiral (or, the twist-bend, N_TB) nematic phase predicted for bent-core mesogens has engendered much interest due to its unique structure and physical properties, and the possibility of use in the next generation of fast electro-optic technology. Bimesogenic calamitic as well as bent-core mesogens are found to form the N_TB phase. Here, we report direct measurements of the temperature dependence of the conical tilt and the evidence of volcano-like orientational distribution of molecules in the N_TB phase. Optical and x-ray scattering investigations of two single-component calamitic bimesogens and their mixtures show that, while the Maier–Saupe orientational distribution function (ODF) is valid for the higher temperature nematic phase, a generalised expansion in terms of even Legendre functions is needed for the N_TB phase. Temperature dependence of the ODFs and the order parameters 〈P₂(cosβ)〉, 〈P₄(cosβ)〉, and 〈P₆(cosβ)〉 has been measured in both phases. The parameters 〈P₂(cosβ)〉 and 〈P₄(cosβ)〉 increase/decrease in the N/N_TB phase with decreasing temperature, while 〈P₆(cosβ)〉 remains vanishingly small for all samples. The value of 〈P₄(cosβ)〉 becomes negative in the N_TB phase confirming a conical distribution of molecules as they follow a helical trajectory keeping the local director tilted at an angle α wrt the macroscopic director. The heliconical tilt calculated from ODFs, exhibits a power law behaviour with temperature, vanishing at the transition to the N phase.     

Synthesis,spectroscopic and X-ray crystallographic properties of manganese compounds of keto- and enol-coordinated di-2-pyridyl ketone benzoyl hydrazone (dpkbh). Reactions of [Mn(CO)5Br] with dpkbh

Reactions between [Mn(CO)₅Br] and dpkbh in low boiling solvents in air gave fac-[Mn^I(CO)₃(κ²-N_py,N_im-dpkbh)Br]·H₂O, [Mn^IIBr₂(κ³-N_py,N_im,O-dpkbh)], and [Mn^II(κ³-N_py,N_im,O-dpkbh-H)₂]·0.5H₂O (N_im = imine nitrogen and N_py = pyridyl nitrogen). Crystallization of fac-[Mn^I(CO)₃(κ²-N_py,N_im-dpkbh)Br]·H₂O from dmso or CH₃CN produced dark red crystals of [Mn^II(κ³-N_py,N_im,O-dpkbh-H)₂]·nX (X = dmso, n = 1 and X = H₂O, n = 0.22). This is in contrast to the reaction of [Re(CO)₅Cl] with dpkbh in refluxing toluene to form fac-[Re^I(CO)₃(κ²-,N_py,N_py-dpkbh)Cl] which can be crystallized from CH₃CN, dmso or dmf to form fac-[Re^I(CO)₃(κ²-,N_py,N_py-dpkbh)Cl]·nX (X = CH₃CN, n = 0 and solvate = dmso or dmf, n = 1). Infrared spectral measurements are consistent with keto coordination of dpkbh to Mn(I) in fac-[Mn^I(CO)₃(κ²-N_py,N_im-dpkbh)Br]·H₂O and Mn(II) in [Mn^IIBr₂(κ³-N_py,N_im,O-dpkbh)] plus enol coordination of the amide-deprotonated dpkbh, to the Mn(II) center in [Mn^II(κ³-N_py,N_im,O-dpkbh-H)₂]·0.5H₂O. Electronic absorption spectral measurements in non-aqueous solvents indicate sensitivity of fac-[Mn^I(CO)₃(κ²-N_py,N_im-dpkbh)Br]·H₂O and [Mn^II(κ³-N_py,N_im,O-dpkbh-H)₂]·0.5H₂O to changes in their outer-shell environments. X-ray crystallographic analyses elucidated the identities of [Mn^IIBr₂(κ³-N_py,N_im,O-dpkbh)] and [Mn^II(κ³-N_py,N_im,O-dpkbh-H)₂]·nX and divulged weaker coordination of [dpkbh] to Mn(II) in [Mn^IIBr₂(κ³-N_py,N_im,O-dpkbh)] and stronger coordination of [dpkbh-H]^? to Mn(II) in [Mn^II(κ³-N_py,N_im,O-dpkbh-H)₂]·0.22H₂O. Low-temperature X-ray structural analyses were employed to account for the disorder in the structure of [Mn^II(κ³-N_py,N_im,O-dpkbh-H)₂] and the short NH bond distance observed in the structure of [Mn^IIBr₂(κ³-N_py,N_im,O-dpkbh)]. A PLATON Squeeze treatment was invoked to account for the fractional occupancy of lattice water in the structure of [Mn^II(κ³-N_py,N_im,O-dpkbh-H)₂].     

Two non-linear azide containing heteronuclear complexes: crystal structure and thermal decomposition

Bis-N,N′(salicylidene)-2,2′-dimethyl-1,3-propanediamine (LDMH₂) has a high tendency to form polynuclear complexes. Two trinuclear complexes were obtained using this ligand and azide ions; (CuLDM)₂ · Mn(N₃)₂ · (DMF)₂, [(C₁₉H₂₀N₂O₂Cu)₂ · Mn(N₃)₂ · (C₃H₇NO)₂] and (CuLDM)₂ · Cd(N₃)₂ · (DMF)₂, [(C₁₉H₂₀N₂O₂Cu)₂ · Cd(N₃)₂ · (C₃H₇NO)₂]. The structures were identified with X-ray methods. TG and DSC methods were also employed to these complexes. Studies showed the (CuLDM)₂ · Mn(N₃)₂ · (DMF)₂ and (CuLDM)₂ · Cd(N₃)₂ · (DMF)₂ to be non-linear. Also μ-bridges were not encountered for the azide ions but were seen to form between the Cu and other metal via phenolic oxygens. Thermal analysis showed exothermic degradation of the azide ions destroying the trinuclear structure. Although azide containing structures show explosive characteristics, this was not observed for the present compounds.     

Synthesis,crystal structures,and fluorescence properties of two dinuclear cadmium(II) complexes derived from <Emphasis Type="Italic">N</Emphasis>-isopropyl-<Emphasis Type="Italic">N</Emphasis>′-(1-pyridin-2-ylethylidene)ethane-1,2-diamine

A new tridentate pyridyl Schiff base, N-isopropyl-N′-(1-pyridin-2-ylethylidene)ethane-1,2-diamine (L), was used to synthesize two dinuclear cadmium(II) complexes, [Cd₂L₂(μ _1,1-N₃)₂(N₃)₂] (1) and [Cd₂L₂(μ _1,3-NCS)₂(NCS)₂] (2). X-ray single crystal structure determination reveals that in both centrosymmetric complexes, the Cd atom is in a distorted octahedral coordination. In the crystal structures of 1 and 2, the dinuclear cadmium(II) complex molecules are linked, respectively, through intermolecular N–H···N and N–H···S hydrogen bonds to form infinite 1D chains. The preliminary fluorescence properties of the complexes were investigated.     

8-Aminoquinoline as a new bidentate ligand for cis-MoO2: synthesis and characterization of a dioxomolybdenum(VI) amide [MoO2(NHC9H6N)2]

The reaction of (Bu₄N)₂[Mo₆O₁₉] with 8-aminoquinoline in the presence of DCC (N,N′-dicyclohexylcarbodiimide) afforded the cis-dioxo-Mo(VI) amide [MoO₂(NHC₉H₆N)₂], which was characterized by spectroscopy, mass spectrometry, ¹H NMR, and single-crystal X-ray analysis. X-ray crystallography shows that the complex exhibits a distorted octahedral geometry with each oxo ligand trans to the quinolyl nitrogen and the amido ligands are bound to the metal in an N,N-chelating fashion. The molecules form zigzag chains via C–H?···?O hydrogen bonds and the chains are connected into networks through interchain N–H?···?O hydrogen bonds.     

The electron-pair density of atomic systems. Rigorous bounds and application to helium

Firstly, the monotonicity properties of the electron-pair densityI(u) of atomic systems are investigated. Leth(u) denote the spherically-averaged electron-pair density of an arbitraryN-electron system, which essentially coincides withI(u) in the case of atoms. It is found that the interelectronic functiong _α(u)=h(u)/u ^α, α≧0, is not only monotonically decreasing from the origin for α≧α₁=max{uh′(u)/h(u)} but it also has the property of convexity for α≧α₂, where the value of α₂ is given in the text. Secondly, the Stieltjes technique is used to obtain rigorous, simple and compact inequalities which involve three interelectronic radial expectation values 〈u ^k 〉. These inequalities are universal in the sense that they are valid for both ground and excited states in the whole periodic table. Thirdly, for those systems with a unimodalh(u), i.e. having a single maximum atu=u _max , are found (i) upper bounds tou _max in terms of any number of moments 〈u ^k 〉 via the above-mentioned technique, and (ii) lower bounds to the maximal valueh _max ≡h(u _max ) by means of two arbitrary moments 〈u ^k 〉 in a variational way. A particular case of the latter bound leads to a rigorous upper bound to the total electro-electron repulsion energyE _ee of the system, namely \(E_{ee} \leqq \left[ {\frac{{9\pi }}{8}N^2 (N - 1)^2 h_{max} } \right]\frac{1}{3}\) . Finally, the electron-pair density of Helium is analysed in detail and the quality of the above mentioned inequalities is studied by means of theM-term Hylleraas-type wavefunctions, withM=1,2,3,6,10 and 20. We observe that in the 20-term case, which is shown to be very close to the exact one, α₁ and α₂ take the values 0.0414 and 0.2067, respectively. Moreover, in such a case we found that some of the above mentioned inequalities are very accurate.     

Experimental Evidence for a Calix[4]arene-Proton Complex

From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium H⁺(aq) + 1 ·Na⁺(nb) ⇆ 1 ·H⁺(nb) + Na⁺(aq) taking place in the two-phase water-nitrobenzene system (1 = p-tert-butylcalix[4]arene-tetrakis(N, N-diethylacetamide); aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K _ex(H⁺, 1 ·Na⁺) = −1.4 ± 0.1. Further, the stability constant of the p-tert-butylcalix[4]arene-tetrakis(N,N-diethylacetamide)-H⁺ complex in water saturated nitrobenzene was calculated for a temperature of 25°C as log β_nb(1 · H⁺) = 8.1 ± 0.1.     

Experimental Evidence for a Calix[4]arene-Proton Complex

Summary. From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium H⁺(aq) + 1 ·Na⁺(nb) ⇆ 1 ·H⁺(nb) + Na⁺(aq) taking place in the two-phase water-nitrobenzene system (1 = p-tert-butylcalix[4]arene-tetrakis(N, N-diethylacetamide); aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K _ex(H⁺, 1 ·Na⁺) = −1.4 ± 0.1. Further, the stability constant of the p-tert-butylcalix[4]arene-tetrakis(N,N-diethylacetamide)-H⁺ complex in water saturated nitrobenzene was calculated for a temperature of 25°C as log β_nb(1 · H⁺) = 8.1 ± 0.1.     

Triple-Helix Formation by Pyrimidine Oligonucleotides Containing Nonnatural Nucleosides with Extended Aromatic Nucleobases: Intercalation from the major groove as a method for recognizing C·G and T · A base pairs

The sequence-specific recognition of double-helical DNA by oligonucleotide-directed triple helix formation is limited primarily to purine tracts. To identify potential lead compounds which are able to extend the sequence repertoire of triple helical complexes, we designed two carbocyclic nucleosides with nucleobases attached via amide bonds. N⁵-[(1R, 2S, 3R, 4R)-3-hydroxy-4-(hydroxymethyl)-2-methoxycyclopentyl]-2-{[(1H-pyrrol-2-yl)carbonyl]-amino}thiazole-5-carboxamide ( L1 ) and 2-benzamido-N⁵-[(1R, 2S, 3R, 4R)-3-hydroxy-4-(hydroxymethyl)-2-methoxycyclopentyl]thiazole-5-carboxamide ( L2 ) were synthesized and incorporated into pyrimidine oligonucleotides. The 2-(trimethylsilyl)ethoxymethyl (SEM) protecting group for the 1H-pyrrole NH was found to be compatible with DNA solid-phase synthesis of pyrimidine Oligonucleotides. By quantitative DNase I footprinting analysis, both nonnatural nucleosides L1 and L2 showed preferential binding of pyrimidine over purine bases: L1 / 2 ·(C·G) ≈ L1 / 2 ·(T · A) > L1 / 2 ·(G·C) ≈ L1 / 2 ·(A · T). Comparison with the previously reported nonnatural nucleosides with extended aromatic nucleobases 1-(2-deoxy-β-D -ribofuranosyl)-4-(3-benzamidophenyl)-imidazole ( D3 ) and N⁴-[6-(benzamido)pyridin-2-yl]-2′-deoxycytidine (^bz M ) suggests that the observed binding selectivity C · G ≈ T · A > G · C ≈ A · T for the nucleoside analogs L1 , L2 , D3 , and ^bz M is derived from sequence-specific intercalation with preferential stacking of their nucleobases over pyrimidine · purine Watson-Crick base pairs.     

Application of the topological analysis of the electronic localization function to archetypical [Pb(II)Ln]p complexes: The bonding of Pb2+ revisited

The coordination of neutral ligands (L = OC, HCN, NH₃, PH₃, SH₂, HNCO and H₂O) to Pb²⁺ is investigated and analyzed by means of the topological analysis of the Electronic Localization Function (ELF). It is shown that the mean charge density of the V(Pb) basin (〈ρ〉_V(Pb)) can reach a ligand‐independent limiting value from n = 6, a coordination number from which the [PbL_n]²⁺ complexes adopt holodirected structures. The investigations performed on anionic series (L = HS^?, OH^?, CN^?, F^?, Cl^?, and Br^?) lead to optimized stable structures in which the coordination number does not exceed n = 4, even in the presence of a model aqueous solvent. This different behavior with respect to the neutral ligand series is interpreted by means of natural populations and electrostatic repulsions. The main result of this contribution is that stable Pb(II) complexes could be those exhibiting reasonable values of 〈ρ〉_V(Pb), namely those not exceeding the saturation plateau evidenced in the present piece of work. © 2009 Wiley Periodicals, Inc. J Comput Chem 2010     

Wavelet transform of quantum chemical states

By using the technique of integral within an ordered product of operators, we recast classical wavelet transform to a matrix element of the squeezing‐displacing operator U(μ,s) between the mother wavelet vector 〈ψ| and the state vector |f〉 to be transformed, i.e., we propose that 〈ψ|U(μ,s)|f〉 can be considered as a new kind of spectrum for analyzing the quantum state |f〉. In this way, we propose the wavelet‐ transform spectrum for quantum chemical states. As an example, we carry out the numerical calculation of wavelet‐transform spectrum for the binomial state. It seems to us that this kind of spectrum can be used to recognize a variety of quantum chemical states. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

Atomic level picture of stress relaxation in polymer melts

We have been developing a physical picture on the atomic level of stress relaxation in polymer melts by means of computer simulation of the process in model systems. In this article we treat a melt of freely jointed chains, each with N = 200 bonds and with excluded-volume interactions between all nonbonded atoms, that has been subjected to an initial constant-volume uniaxial extension. We consider both the stress relaxation history σ(t) based on atomic interactions, and the stress history σ_e(t; N_R) based on subdividing the chain into segments with N_R bonds each, with each segment regarded as an entropic spring. It is found that at early times σ(t) > σ_e(t; N_R) for all N_R, and that, for the remainder of the simulation, there is no value of N_R for which σ(t) = σ_e(t; N_R) for an extended period; by the end of the simulation σ(t) has fallen just below the value σ_e(t; 50). The decay of segment orientation, 〈P₂(t; N_R)〉, and of bond orientation 〈P₂(t; 1)〉, is computed during the simulation. It is found that the decay of the atom-based stress σ(t) is closely related to that of 〈P₂(t; 1)〉. This result may be understood through the concept of steric shielding. The change in local structure of the polymer melt during relaxation is also studied. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36 : 143–154, 1998     

Semiempirical local spin: Theory and implementation of the ZILSH method for predicting Heisenberg exchange constants of polynuclear transition metal complexes

The local spin formalism ( 3 ) for computing expectation values 〈S_A · S_B〉 that appear in the Heisenberg spin model has been extended to semiempirical single determinant wave functions. An alternative derivation of expectation values in restricted and unrestricted cases is given that takes advantage of the zero differential overlap (ZDO) approximation. A formal connection between single determinant wave functions (which are not in general spin eigenfunctions) and the Heisenberg spin model was established by demonstrating that energies of single determinants that are eigenfunctions of the local spin operators with eigenvalues corresponding to high‐spin radical centers are given by the same Heisenberg coupling constants {J_AB} that describe the true spin states of the system. Unrestricted single determinant wave functions for transition metal complexes are good approximations of local spin eigenfunctions when the metal d orbitals are local in character and all unpaired electrons on each metal have the same spin (although spins on different metals might be reversed). Good approximations of the coupling constants can then be extracted from local spin expectation values 〈S_A · S_B〉 energies of the single determinant wave functions. Once the coupling constants are obtained, diagonalization of the Heisenberg spin Hamiltonian provides predictions of the energies and compositions of the spin states. A computational method is presented for obtaining coupling constants and spin‐state energies in this way for polynuclear transition metal complexes using the intermediate neglect of differential overlap Hamiltonian parameterized for optical spectroscopy (INDO/S) in the ZINDO program. This method is referred to as ZILSH, derived from ZINDO, Davidson's local spin formalism, and the Heisenberg spin model. Coupling constants and spin ground states obtained for 10 iron complexes containing from 2 to 6 metals are found to agree well with experimental results in most cases. In the case of the complex [Fe₆O₃(OAc)₉(OEt)₂(bpy)₂]⁺, a priori predictions of the coupling constants yield a ground‐state spin of zero, in agreement with variable‐temperature magnetization data, and corroborate spin alignments proposed earlier on the basis of structural considerations. This demonstrates the potential of the ZILSH method to aid in understanding magnetic interactions in polynuclear transition metal complexes. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003     

Two binuclear complexes containing the enrofloxacinate anion: Cd2(C19H21N3O3F)4(H2O)2 · 4H2O and Pb2(C19H21N3O3F)4 · 4H2O

The syntheses and crystal structures of the closely related but non-isostructural Cd₂(C₁₉H₂₁N₃O₃F)₄(H₂O)₂?·?4H₂O (1) and Pb₂(C₁₉H₂₁N₃O₃F)₄?·?4H₂O (2) are described, where C₁₉H₂₁N₃O₃F^? is enrofloxacinate (enro). Both compounds contain centrosymmetric, binuclear, neutral complexes incorporating a central diamond-shaped M₂O₂ (M?=?Cd, Pb) structural unit. The Cd²⁺ coordination polyhedron in 1 is a CdO₆ trigonal prism, including one coordinated water. The Pb²⁺ coordination polyhedron in 2 can be described as a very distorted square-based PbO₅ pyramid, although two additional short Pb?···?O (<3.1?Å) contacts are also present. In the crystal of the cadmium complex, O–H?···?O hydrogen bonds lead to a layered structure. In the lead compound, O–H?···?O and O–H?···?N interactions lead to chains in the crystal. Crystal data: 1: C₇₆H₉₆Cd₂F₄N₁₂O₁₈, M _r?=?1766.45, triclinic, P 1, a?=?12.185(2)?Å, b?=?12.306(3)?Å, c?=?14.826(3)?Å, α?=?68.15(3)°, β?=?70.28(3)°, γ?=?86.11(3)°, V?=?1938.2(7)?ų, Z?=?1, T?=?298 K, R(F)?=?0.030, wR(F ²)?=?0.079. 2: C₇₆H₈₈F₄N₁₂O₁₆Pb₂, M _r?=?1920.00, triclinic, P 1, a?=?12.0283(4)?Å, b?=?12.7465(4)?Å, c?=?13.0585(4)?Å, α?=?83.751(1)°, β?=?74.635(1)°, γ?=?81.502(1)°, V?=?1904.3(1)?ų, Z?=?1, T?=?298?K, R(F)?=?0.021, wR(F ²)?=?0.049.     

Comparative X‐ray study of three nickel(II)–thio­cyanate compounds

Three cis nickel–di­thio­cyanate (SCN) complexes with different N,N′‐bidentate bases have been prepared and their crystal structures determined: bis(2,2′‐bi­pyridine‐N,N′)­bis­(thio­cyan‐­ato‐N)­nickel(II), [Ni(SCN)₂­(C₁₀H₈N₂)₂], bis(1,10‐phen­anthroline‐N,N′)­bis­(thio­cyanato‐N)­nickel(II), [Ni(SCN)₂­(C₁₂H₈N₂)₂], and bis(2,9‐di­methyl‐1,10‐phenanthroline‐N,N′)­bis­(thiocyanato‐N)nickel(II) mono­hydrate, [Ni(SCN)₂­(C₁₂H₈N₂)₂]·H₂O. Distortions due to ligand size are discussed.     

Structural study of six cycloalkylammonium cinnamate salt structures featuring one‐dimensional columns and two‐dimensional hydrogen‐bonded networks

Six ammonium carboxylate salts, namely cyclopentylammonium cinnamate, C₅H₁₂N⁺·C₉H₇O₂⁻, (I), cyclohexylammonium cinnamate, C₆H₁₄N⁺·C₉H₇O₂⁻, (II), cycloheptylammonium cinnamate form I, C₇H₁₆N⁺·C₉H₇O₂⁻, (IIIa), and form II, (IIIb), cyclooctylammonium cinnamate, C₈H₁₈N⁺·C₉H₇O₂⁻, (IV), and cyclododecylammonium cinnamate, C₁₂H₂₆N⁺·C₉H₇O₂⁻, (V), are reported. Salts (II)–(V) all have a 1:1 ratio of cation to anion and feature three N⁺—H...O⁻ hydrogen bonds forming one‐dimensional hydrogen‐bonded columns consisting of repeating R₄³(10) rings, while salt (I) has a two‐dimensional network made up of alternating R₄⁴(12) and R⁶₈(20) rings. Salt (III) consists of two polymorphic forms, viz. form I having Z′ = 1 and form II with Z′ = 2. The latter polymorph has disorder of the cycloheptane rings in the two cations, as well as whole‐molecule disorder of one of the cinnamate anions. A similar, but ordered, Z′ = 2 structure is seen in salt (IV).     

Two solvent directed zinc(II) coordination polymers with 1-D single-zigzag chain and 1-D double-zigzag chains

Two coordination polymers, {[Zn(NiL)(DMA)(H₂O)₂] (DMA)(H₂O)} _n (1) (DMA?=?N,N-dimethylacetamide) and {[Zn₂(NiL)₂(DMF)(H₂O)₄]?·?3DMF} _n (2) (DMF?=?N,N-dimethylformamide), have been prepared by reactions of Zn(NO₃)₂?·?6H₂O and NiL in CH₂Cl₂-DMA–H₂O and CH₂Cl₂-DMF–H₂O, respectively. H₂L denotes dimethyl 5,6,7,8,15,16-hexahydro-6,7-dioxodibenzo-9,10-benzo-[1,4,8,11]tetraazacyclotetradecine-13,18-dicarboxylate. Single-crystal X-ray diffraction analyses reveal that coordination geometries around Ni(II) are identical with slightly distorted square planar and all Ni–N bonds are very short. Complex 1 shows 1-D zigzag chain structure, while 2 has 1-D double-zigzag chains. The chains, which are packed parallel in 1 and 2, are interconnected by lattice solvent through O–H···O and C–H···O hydrogen bonds to form 3-D supramolecular networks. We discuss solvent effects on assembly of the two coordination polymers. The results reveal that coordinated solvent has influence on the assembly procedure.     

Two new dimeric cadmium(II) and zinc(II) sulfate complexes with 2,4,6‐tris(2‐pyridyl)‐1,3,5‐triazine and 2,2:6′,2′′‐ter­pyridine

The structures of two new sulfate complexes are reported, namely di‐μ‐sulfato‐κ³O,O′:O′′‐bis{aqua­[2,4,6‐tris(2‐pyridyl)‐1,3,5‐triazine‐κ³N¹,N²,N⁶]­cadmium(II)} tetra­hydrate, [Cd₂(SO₄)₂(C₁₆H₁₂N₆)₂(H₂O)₂]·4H₂O, and di‐μ‐sulfato‐κ²O:O′‐bis­[(2,2′:6′,2′′‐ter­pyridine‐κ³N¹,N^1′,N^1′′)­zinc(II)] dihydrate, [Cd₂(SO₄)₂(C₁₅H₁₁N₃)₂]·2H₂O, the former being the first report of a Cd(tpt) complex [tpt is 2,4,6‐tris(2‐pyridyl)‐1,3,5‐triazine]. Both compounds crystallize in the space group P and form centrosymmetric dimeric structures. In the cadmium complex, the metal center is heptacoordinated in the form of a pentagonal bipyramid, while in the zinc complex, the metal ion is in a fivefold environment, the coordination geometry being intermediate between square pyramidal and trigonal bipyramidal. Packing of the dimers leads to the formation of planar structures strongly linked by hydrogen bonding.