Structure and conformational properties of carbonylbisimidosulfuryl fluoride, O=C(N=S(O)F2)2

The molecular structure and conformational properties of O=C(N=S(O)F₂)₂ (carbonylbisimidosulfuryl fluoride) were determined by gas electron diffraction (GED) and quantumchemical calculations (HF/3-21G* and B3LYP/6-31G*). The analysis of the GED intensities resulted in a mixture of 76(12)% syn–syn and 24(12)% syn–anti conformer (ΔH⁰=H⁰(syn–anti)−H⁰(syn–syn)=1.11(32) kcal mol⁻¹) which is in agreement with the interpretation of the IR spectra (68(5)% syn–syn and 32(5)% syn–anti, ΔH⁰=0.87(11) kcal mol⁻¹). syn and anti describe the orientation of the S=N bonds relative to the C=O bond. In both conformers the S=O bonds of the two N=S(O)F₂ groups are trans to the C–N bonds. According to the theoretical calculations, structures with cis orientation of an S=O bond with respect to a C–N bond do not correspond to minima on the energy hyperface. The HF/3-21G* approximation predicts preference of the syn–anti structure (ΔE=−0.11 kcal mol⁻¹) and the B3LYP/6-31G* method results in an energy difference (ΔE=1.85 kcal mol⁻¹) which is slightly larger than the experimental values. The following geometric parameters for the O=C(N=S)₂ skeleton were derived (r_a values with 3σ uncertainties): C=O 1.193 (9) Å, C–N 1.365 (9) Å, S=N 1.466 (5) Å, O=C–N 125.1 (6)° and C–N=S 125.3 (10)°. The geometric parameters are reproduced satisfactorily by the HF/3-21G* approximation, except for the C–N=S angle which is too large by ca. 6°. The B3LYP method predicts all bonds to be too long by 0.02–0.05 Å and the C–N=S angle to be too small by ca. 4°.     

Simulated T ← S spectra of benzaldehydes as a function of the energy gap between the ππ and nπ levels

The T_1,2 ← S₀ spectra of benzaldehydes have been studied as a function of the energy separation between the vibrationless levels. It is shown that the spectra are very complicated in the region of ΔE[T₂⁰(nπ^*)-T₁⁰(ππ^*)] = 250–400 cm⁻¹, reflecting effective vibronic interferences between T₂⁰(0-0) and each of the ν₃₆-ν₃₃ out-of-plane vibrational levels of T₁⁰(ππ^*). The simulated spectra correspond to the observed spectra. In the case of T₁⁰ = ³nπ^* and T₂⁰ = ³ππ^* the spectral change is not so drastic as in the reverse case loc. cit. because the optical intensity generally concentrates in the longest wavelength band, i.e., the origin band of the T₁(nπ^*) ← S₀ transition. The simulation spectra are useful for interpretation of the absorption spectra in similar electronic structure systems of substituted benzaldehydes.     

Predissociation of chlorobenzene, beyond the pseudo-diatomic model

Dissociation of chlorobenzene via the lowest singlet excited state has been investigated by means of pump–probe femtosecond spectroscopy and spin–orbit corrected ab initio quantum chemistry. We have found that the so far accepted model with a ¹ππ^* → ³π/nσ^* reaction mechanism has to be amended. We suggest that the mechanism goes via a transition from ¹ππ^* to a πσ^* state that is to 90% a singlet. Further, three nuclear degrees of freedom required to describe the dissociation have been defined.     

Ab initio structural trends and torsional sensitivity in n-hexane and comparisons with crystallographic structural results

The molecular structures of n-hexane were determined by RHF/4-21G ab initio geometry optimization at 30° grid points in its three-dimensional τ₁(C11–C8–C5–C1), τ₂(C14–C11–C8–C5), τ₃(C17–C14–C11–C8) conformational space. Of the resulting 12×12×12=1728 grid structures, 468 are symmetrically non-equivalent and were optimized constraining the torsions τ₁, τ₂, and τ₃ to the respective grid points, while all other structural parameters were relaxed without any constraints. From the results, complete parameter surfaces were constructed using natural cubic spline functions, which make it possible to calculate parameter gradients, |P|=[(∂P/∂τ_i)²+(∂P/∂τ_j)²]^1/2, where P is a C–C bond length or C–C–C angle. The parameter gradients provide an effective measure of the torsional sensitivity of the system and indicate that dynamic activities in one part of the molecule can significantly affect the density of states, and thus the contributions to vibrational entropy, in another part. This opens the possibility of dynamic entropic conformational steering in complex molecules; i.e. the generation of free energy contributions from dynamic effects of one part of a molecule on another. When the conformational trends in the calculated C–C bond lengths and C–C–C angles are compared with average parameters taken from some 900 crystallographic structures containing n-hexyl fragments or longer C–C bond sequences, some correlation between calculated and experimental trends in angles is found, in contrast to the bond lengths for which the two sets of data are in complete disagreement. The results confirm experiences often made in crystallography. That is, effects of temperature, crystal structure and packing, and molecular volume effects are manifested more clearly in bond lengths than bond angles which depend mainly on intramolecular properties. Frequency analyses of the τ₁, τ₂ and τ₃ torsional angles in the crystal structures show conformational steering in the sense that, if τ₁ is trans peri-planar (170°≤τ₁≤180°; −180°≤τ₁≤−170°), the values of τ₂ and τ₃ are clustered closely around the ideal gauche (±60°) and trans (±180°) positions. In contrast, when τ₁ is in the region (50°≤τ₁≤70°), there is a definite increase in the populations of τ₂ and τ₃ at −90 and −150°.     

S2 → S0 fluorescence in an aromatic thioketone, xanthione

In addition to the red phosphorescence (T₁(³ A₂n, π^*) → S₀) xanthione exhibits in solution an emission with a maximum at ≈ 23 000 cm⁻¹ and φ_f(298°) = 5 × 10⁻³. It is shown that this emission is fluorescence from the second excited singlet state (S₂ (¹A₁ π, π^*) → S₀).     

Molecular structure and conformational stability of allylisocyanate—post-Hartree–Fock and density functional theory studies

The molecular structure and conformational stability of allylisocyanate (CH₂CHCH₂NCO) molecule was studied using the ab initio and DFT methods. The geometries of possible conformers, C-gauche (δ=120°, θ=0°) (δ=C=C–C–N and θ=C–C–N=C) and C-cis N-trans (δ=0° and θ=180°) were optimized employing HF/6-31G^*, MP2/6-31G^* levels of theory of ab initio and BLYP, B3LYP, BPW91 and B3PW91 methods of DFT implementing the atomic basis set 6-311+G(d,p). The structural and physical parameters of the above conformers were discussed with the experimental and theoretical values of the related molecules, methylisocyanate and 3-fluoropropene. It has been found that the N=C=O bond angle is not linear as the experimental result for both the conformers and the theoretical bond angle is 173°. The rotational potential energy surfaces have been performed at the HF/6-31G^*, and MP2/6-31G^* levels of theory. The Fourier decomposition potentials were analysed at the HF/6-31G^*, and MP2/6-31G^* levels of theory. The HF/6-31G^* level of theory predicted that the C-gauche conformer is more stable than the C-cis N-trans conformer by 0.41 kJ/mol, but the MP2 and DFT methods predicted the C-cis N-trans conformer is found to be more stable than the C-gauche conformer. The calculated chemical hardness value at the HF/6-31G^* level of theory predicted the C-cis N-trans form is more stable than C-gauche form, whereas the chemical hardness value at the MP2/6-31G^* level of theory favours the slight preference towards the C-gauge conformer.     

Structural characterisation of [Pt(NH3)4]2[W(CN)8][NO3]·2H2O donor–acceptor complex

The bimetallic [Pt(NH₃)₄]₂[W(CN)₈][NO₃]·2H₂O is characterised by single-crystal X-ray diffraction [S.G.P2₁/m(11), a=8.0418(7), b=19.122(2), c=9.0812(6) Å, Z=2]. All platinum centres have the square-plane D_4h geometry with average dimensions Pt(1)–N 2.042(2) and Pt(2)–N 2.037(10) Å. The octacyanotungstate anion has the square-antiprismatic D_4d configuration with average dimensions W(1)–C 2.164(13), C–N 1.140(12), W(1)–N 3.303(5) Å. The structure exhibits two different mutual orientations of Pt versus W units resulting in Pt(2)–W(1), W(1)^* separations of 4.77(2), 4.55(2)^* and Pt(1)–W(1) of 6.331(8) Å. A centrosymmetric structure reveals groups of two distinct columns: the first is formed by intercalated NO₃⁻ between parallel [Pt(1)(NH₃)₄]²⁺ planes and the second consists of [W(CN)₈]³⁻ interlayered by, parallel to square faces of W-antiprisms, [Pt(2)(NH₃)₄]²⁺. The structure is stabilised through a three-dimensional hydrogen bond network via nitrogen atoms of cyanide ligands, hydrogen atoms of NH₃ ligands, water molecules and oxygen atoms of NO₃⁻ counteranions. The vibrational pattern and the range of ν(CN) frequencies attributable to the electronic environment of W(V) and W(IV) are consistent with the ground state Pt(II)↔W(V) charge transfer.     

A study on copper(II)-Schiff base-azide coordination complexes: Synthesis, X-ray structure and luminescence properties of [Cu(L)(N3)]X (L = Schiff bases; X = ClO4, PF6)

Two Schiff bases N,N′-(bis(pyridin-2-yl)benzylidene)propane-1,3-diamine (pbpd) and N,N′-(bis(pyridin-2-yl)formylidene)butane-1,4-diamine (pfbd) have been prepared and used to synthesize copper(II) complexes. Four complexes of the type [Cu(L)(N₃)]X (1–4) [L = pbpd; X = ClO₄ (1); L = pbpd; X = PF₆ (2); L = pfbd; X = ClO₄ (3); L = pfbd; X = PF₆ (4)] have been synthesized and characterized on the basis of microanalytical, spectroscopic, magnetic, electrochemical, luminescence and other physicochemical properties. Two representative complexes of the series, 2 and 3, have been characterized by single crystal X-ray diffraction measurements which reveal that in each complex the copper(II) ion assumes a distorted trigonal bipyramidal environment through coordination of the metal centre by two pyridine N atoms and two imine N atoms of the Schiff base with the fifth position occupied by a N atom of a terminal . They display intraligand ¹(π–π^*) fluorescence at room temperature and intraligand ³(π–π^*) phosphorescence in glassy solutions (MeOH at 77 K). A band (492 nm) observed for the complexes in their solid-state emission spectra is an excimeric emission arising due to an aromatic π–π interaction. Electrochemical electron transfer study reveals Cu^II–Cu^I reduction in methanolic solutions.     

MRD CI study on the low-lying states of AlP

Large-scale MRD CI calculations assign to AlP the ground state X ³Σ⁻ (9σ²3π²) and a close-lying state 1 ³Π (9σ3π³) (T_e = 0.08 eV). Up to transition energies of 2.0 eV, other states are described by the configurations 9σ3π³ (1¹Π), 8σ²3π⁴ (1 ¹Σ⁺), 9σ²3π² (1 ¹Δ and 2 ¹Σ⁺) and 9σ3π²4π (1 ⁵Π). The 2 ³Π state, located at ≈ 2.30 eV, shows a shallow double minimum. Numerous perturbations are expected to induce predissociation upon 2 ³Π. Multiplets arising from the occupation 8σ²3π³4π are clustered in the 3.25–3.50 eV region. Quintet states with the configuration 8σ9σ3π³4π are bound, with T_e values (in eV) of 3.80 (1 ⁵Σ⁺), 4.44 (1 ⁵Δ) and 4.88 (3 ⁵Σ⁻), respectively. The 9σ → 4s Rydberg members ⁵Σ⁻ and ³Σ⁻ lie in the 4.58–4.72 eV energy region. The first ionization potential (ionization to X⁴Σ⁻ of AlP⁺, 9σ → ∞) is estimated to be 7.65 eV. Ionization to the 1 ²Σ⁻ and 1 ²Π states of AlP⁺ is suggested to occur between 8.0 and 8.8 eV. The dipole moments of X ³Σ⁻, 1 ¹Δ and 2 ¹Σ⁺ are close to 1.0 D, whereas the 1 ¹Σ⁺ state has μ = 3.49 D; 1 ³Π and 1 ¹Π have dipole moments from 2.45 to 2.91 D. All low-lying states show a polarity Al⁺P⁻. Finally, the electronic structure and transition energies of AlP are compared with those of the isoelectronic species BN, AIN, and SiP⁺.     

Spectroscopic study of harmane in micelles at 77 K using fluorescent probes

Steady-state and time-resolved emission for spectroscopic techniques at 77 K, and molecular orbital calculations using PM3-MOPAC/93 and HAM/3-CI have been used to study the two forms of harmane, the neutral (HN) and the monoprotonated (HH), in different environments. In hydrophobic media, for (HN), four species were determined and in hydrophilic medium, for (HH), we found just one species. The photophysical properties of all these species were determined, and we verified that each one of them displays distinct photophysical properties from one to another. For example, for monomer of (HN), the lowest electronic singlet state S₁ is (π,π^*) and the lowest electronic triplet state T₁ is (π,π^*), due to the phosphorescence lifetime it is t=0.8 s. For the (HH) monomer, the S₁ is (π,π^*) and T₁ is (π,π^*) and the spin–orbital coupling is inefficient. These determinations were used to characterise and to identify the harmane species that is solubilised into the interior of neutral (triton X-100), anionic (dodecyl lithium sulphate) and cationic (hexadecyltrimethyl ammonium bromide) micelles, all of them were prepared under physiological conditions. The results indicated that active species in the interior of the micelles is a hydrogen bond complex between (HN) and micellar environments that is anchored in the aqueous region of micelles.     

Ab initio study of anomeric effect in 2,2-difluoroglycine

The optimized molecular structures of seven conformations of 2,2-difluoroglycine have been obtained from ab initio calculations. For conformers in which the lone pair of electrons on the nitrogen are antiperiplanar to one of the C–F bonds, that C–F bond is longer than the other C–F bond, which is synperiplanar to the lone pair of electrons. Conformers which have these features are the most stable conformers of those examined. This observation is explained in terms of an anomeric effect of the 1p(N)→σ^*(C–F). At the MP2/6-31G^* level of calculation, conformers IV and V are 21.5 and 18.7 kJ/mol, respectively, more stable than the least stable conformer, VI, which does not exhibit an anomeric effect. Conformer VII was found to be exceptionally stable, in addition to an anomeric effect, this conformer also exhibits features of a FH–O hydrogen bond.     

The H method: hydrogen atoms with a fictitious nuclear charge. A versatile theoretical tool for study of atom and group properties as substituents: electronegativity and partition of σ and π contributions

We present a preliminary work for a general method of computing the partition of σ and π electronic effects of a given atom A or substituent R on a given substrate. In this aim, the nuclear charge Z^* of a fictitious hydrogen atom H^* is fitted in order that the A–H^* (or R–H^*) bond be purely covalent, i.e. the Mulliken electron population be one electron on H^*. We obtain this way entities of the same electronegativity as A or R, thus having a comparable σ effect, without any π effect.

The values of Z^* obtained for A–H^* diatomic molecules (A=H–Br) exhibit a good linear correlation with the Allred–Rochow scale of electronegativity, as it could be expected on theoretical grounds. The method, applied to R–H^* molecules, allows a determination of the electronegativity of a variety of polyatomic R substituents, and provides H^*(R) having the same inductive effect as R. These results are discussed by comparison with some previous theoretical and experimental data.

As an example of application, the partition of σ and π contributions of R on the ¹³C chemical shifts in a series of monosubstituted benzenes RC₆H₅ has been computed.     

Synthesis and crystal structure of 9,10-dihydro-9,10-etheno-1,8-dichloro-11-diphenylphosphinyl-12-(diphenylphosphinylethynyl)anthracene

The title compound, 9,10-dihydro-9,10-etheno-1,8-dichloro-11-diphenylphosphinyl-12-(diphenylphosphinylethynyl)anthracene (1), has been synthesized and its crystal structure has been determined. The compound 1 crystallized into the triclinic space group P-1 with =74.837(4)°, β=88.156(4)°, γ=65.398(4)°, Z=2, D_c=1.352 gcm⁻³. In the crystal structure of 1a, one chloroform molecule was included by the compound 1 with a 1:1 ratio and the existence of non-classical intermolecular C–HO hydrogen bonds, intramolecular C–HCl and C–HO hydrogen bonds and π–π stacking were observed.     

Excited state geometries within time-dependent and restricted open-shell density functional theories

Singlet excited state geometries of a set of medium sized molecules with different characteristic lowest excitations are studied. Geometry optimizations of excited states are performed with two closely related restricted open-shell Kohn–Sham methods and within linear response to time-dependent density functional theory. The results are compared to wave-function based methods. Excitation energies (vertical and adiabatic) calculated from the open-shell methods show systematic errors depending on the type of excitation. However, for all states accessible by the restricted methods a good agreement for the geometries with time-dependent density functional theory and wave-function based methods is found. An analysis of the energy with respect to the mixing angle for the singly occupied orbitals reveals that some states (mostly [n→π^*]) are stable when symmetry constraints are relaxed and others (mostly [π→π^*]) are instable. This has major implications on the applicability of the restricted open-shell methods in molecular dynamics simulations.     

Heteroleptic platinum(II) complexes of macrocyclic thioethers and halides: the crystal structures of [Pt(9S3)Cl2], [Pt(9S3)Br2], and [Pt(9S3)I2]

The synthesis, spectroscopic, and crystal structures of three heteroleptic thioether/halide platinum(II) (Pt(II)) complexes of the general formula [Pt(9S3)X₂] (9S3=1,4,7-trithiacyclononane, X=Cl⁻, Br⁻, I⁻) are presented. All three 9S3/dihalo complexes form very similar structures in which the Pt(II) center is surrounded by a cis arrangement of two halides and two sulfur atoms from the 9S3 ligand. The third sulfur from the 9S3 forms a long distance interaction with the Pt center resulting in an elongated square pyramidal structure with a S₂X₂+S₁ coordination geometry. The distances between the Pt(II) center and axial sulfur shorten with larger halide ions (Cl⁻=3.260(3) Å>Br⁻=3.243(2) Å>I⁻=3.207(2) Å). These distances are consistent with the halides functioning as π donor ligands, and their Pt---S axial distances fall intermediate between Pt(II) thioether complexes involving π acceptor and σ donor ligands. The ¹⁹⁵Pt NMR chemical shift values follow a similar trend with an increased shielding of the platinum ion with larger halide ions. The 9S3 ligand is fluxional in all of these complexes, producing a single carbon resonance. Additionally, a related series of homoleptic crown thioether complexes have been studied using ¹⁹⁵Pt NMR, and there is a strong correlation between the chemical shift and complex structure. Homoleptic crown thioethers show the anticipated upfield chemical shifts with increasing number of coordinated sulfurs. Complexes containing four coordinated sulfur donors have chemical shifts that fall in the range of −4000 to −4800 ppm while a value near −5900 ppm is indicative of five coordinated sulfurs. However, for S₄ crown thioether complexes, differences in the stereochemical orientation of lone pair electrons on the sulfur donors can greatly influence the observed ¹⁹⁵Pt NMR chemical shifts, often by several hundred ppm.     

Photophysics of inter- and intra-molecularly hydrogen-bonded systems: Computational studies on the pyrrole–pyridine complex and 2(2′-pyridyl)pyrrole

The role of electron and proton transfer processes in the photophysics of hydrogen-bonded molecular systems has been investigated with ab initio electronic-structure calculations. We discuss generic mechanisms of the photophysics of a hydrogen-bonded aromatic pair (pyrrole–pyridine), as well as an intra-molecularly hydrogen-bonded π system composed of the same molecular sub-units (2(2′-pyridyl)pyrrole). The reaction mechanisms are discussed in terms of excited-state minimum-energy paths, conical intersections and the properties of frontier orbitals. A common feature of the photochemistry of these systems is the electron-driven proton transfer (EDPT) mechanism. In the hydrogen-bonded complex, a highly polar charge transfer state of ¹ππ^* character drives the proton transfer, which leads to a conical intersection of the S₁ and S₀ surfaces and thus ultrafast internal conversion. In 2(2′-pyridyl)pyrrole, out-of-plane torsion is additionally needed for barrierless access to the S₁–S₀ conical intersection. It is pointed out that the EDPT process plays an essential role in the fluorescence quenching in hydrogen-bonded aromatic complexes, the function of organic photostabilizers, and the photostability of biological molecules.     

X–H rotational-echo double-resonance NMR for torsion angle determination of peptides

C–H and N–H rotational-echo double-resonance (REDOR) NMR is developed for determining torsion angles in peptides. The distance between an X spin such as ¹³C or ¹⁵N and a proton is measured by evolving the proton magnetization under REDOR-recoupled X–H dipolar interaction. The proton of interest is selected through its directly bonded heteronuclear spin Y. The sidechain torsion angle χ₁ is extracted from a ¹³Cβ-detected Hβ–N distance, while the backbone torsion angle φ is extracted from an ¹⁵N-detected H^N–C^′ distance. The approach is demonstrated on three model peptides with known crystal structures to illustrate its utility.     

Theoretical investigations of the substituent effect on the absorption and emission properties for a series of platinum (II) complexes supported by tetradentate N2O2 chelates

The photophysical properties, which vary as R is varied, of a series of [Pt(N₂O₂)] complexes bearing bis(phenoxy)bipyridine auxiliaries with different substituents R=H (Pt-H) (1), 4,4′-2NH₂ (Pt-NH₂) (2), 4,4′-2tBu (Pt-tBu) (3), 4,4′-2CN (Pt-CN) (4), and 4,4′-2NO₂ (Pt-NO₂) (5) are investigated using density functional theory (DFT) and time-dependent density functional theory (TDDFT). The solvent effects are discussed in CH₂Cl₂, CH₃CN and CH₃OH solutions, respectively, by polarizable continuum model (PCM). It is anticipated that compared with σ-donor substituents, π-acceptors have more dramatic effects on the electronic and optical properties in this series of complexes. Introduction of π-electron withdrawing substituents on bipyridine ligand will benefit the LLCT (or MLCT) and prohibit the non-radiative pathways via d–d transitions by increasing the energy gap between the HOMO–LUMO and d–d transitions. The results also reveal that the lowest-energy excitations of all complexes show blue-shifts in the polarized solution and when the polarity of the solvent increases from CH₂Cl₂, CH₃CN and CH₃OH, the low-energy broad absorption band exhibit blue-shifts. The lowest-energy excitations and photoluminescence of all complexes are dominated by π(phenoxy)→π^*(bpy/NO₂) (LLCT) excited state mixed with some energetically dπ (Pt)→π^*(bpy/NO₂) (MLCT) transition.     

Monodentate and bidentate trifluoroacetato ligands in bis(trifluoroacetato)-(N-methyl-meso-tetraphenylporphyrinato)thallium(III)—a new dynamic 4:3 piano stool seven-coordinate geometry

The crystal structure of bis(trifluoroacetato)-(N-methyl-meso-tetraphenylporphyrinato) thallium(III), Tl(N---Me---tpp)(CF₃CO₂)₂ (2), was established and the coordination sphere around the Tl³⁺ ion is described as 4:3 tetragonal base–trigonal base piano stool seven-coordinate geometry in which the two cis CF₃CO₂ ⁻ groups occupy two apical sites. The plane of the three pyrrole nitrogen atoms [i.e. N(2), N(3) and N(4)] strongly bonded to Tl³⁺ is adopted as the reference plane 3N. The pyrrole N(1) ring bearing the methyl group [i.e. C(45)H₃] is the most deviated one from the 3N plane making a dihedral angle of 23.3° whereas smaller angles of 9.9, 2.7 and 4.7° occur with pyrroles N(2), N(3), and N(4), respectively. Because of the larger size of the thallium(III) ion, Tl is considerably out of the 3N plane; its displacement of 1.02 Å is in the same direction as that of the two apical CF₃CO₂ ⁻ ligands. The intermolecular trifluoroacetate exchange process for 2 in CD₂Cl₂ solvent is examined through ¹⁹F and ¹³C NMR temperature-dependent measurements. In the slow-exchange region, the CF₃ and carbonyl (CO) carbons of the CF₃CO₂ ⁻ groups in 2 are separately located at δ 114.3 [¹J(C–F)=290 Hz, ³J(Tl–C)=411 Hz] and 155.1 [²J(C–F)=37 Hz, ²J(Tl–C)=204 Hz], respectively, at −106 °C. In the same slow-exchange region, the fluorine atoms of 2, Tl(N---Me---tpp)(CF₃CO₂)⁺ and the free CF₃CO₂ ⁻ are located at δ −73.76 [⁴J(Tl–F)=44 Hz], −73.30 [⁴J(Tl–F)=22 Hz], and −76.15 ppm at −97 °C, respectively.     

3D H-bonding networks self-assembly from pyridinium derivatives and bis(maleonitriledithiolato)zincate(II)

The two ion-pair complexes, [pyH]₂[Zn(mnt)₂] (1) and [4,4′-bipyH₂]-[Zn(mnt)₂] (2), were synthesized, where mnt²⁻ denotes maleonitriledithiolate, and [pyH]⁺, [4,4′-bipyH₂]²⁺ represent pyridinium and diprotonated 4,4′-bipyridinium, respectively. Their single crystal structures show that there are strong bifurcated H-bonding interactions between the cations of the pyridinium derivative and the [Zn(mnt)₂]²⁻ anions in both 1 and 2. The bifurcated H-bonding interactions between the N–H of the pyridiniums and the CN groups of the mnt²⁻ ligands give rise to a 2D layered H-bonding network, the adjacent layers come together in such way as mutual embrace to give a tight pack, thus 2D hydrogen-bonding sheets further develop into 3D H-bonding networks through weak C–HS and ππ stacking interactions in 1. As for 2, the cations and anions connect into several types of H-bonding macrorings ([2+2], [3+3] and [4+4]), these H-bonding macrorings fuse to extend into 2D layered structure, the interpenetration between [3+3] and [4+4] type H-bonding macrorings in the adjacent layers give further rise to novel 3D extended H-bonding networks, in which there are clearly parallel stacks of cations and the chelate rings of anions.