An ab initio theoretical prediction: an antiaromatic ring pi-dihydrogen bond accompanied by two secondary interactions in a "wheel with a pair of pedals" shaped complex FH . . . C4H4 . . . HF

By the counterpoise-correlated potential energy surface method (interaction energy optimization), the structure of the pi H-bond complex FH cdots, three dots, centered FH . . . C4H4 . . . HF has been obtained at the second-order M?ller-Plesset perturbation theory (MP2/aug-cc-pVDZ) level. Intermolecular interaction energy of the complex is calculated to be -7.8 kcal/mol at the coupled-cluster theory with single, double substitutions and perturbatively linked triple excitations CCSD (T)/aug-cc-pVDZ level. The optimized structure is a "wheel with a pair of pedals" shaped (1mid R:1) structure in which both HF molecules almost lie on either vertical line passing through the middle-point of the C[Double Bond]C bond on either side of the horizontal plane of the C4 ring for cyclobutadiene. In the structure, an antiaromatic ring pi-dihydrogen bond is found, in which the proton acceptor is antiaromatic 4 electron and 4 center pi bond and the donors are both acidic H atoms of HF molecules. In accompanying with the pi-dihydrogen bond, two secondary interactions are exposed. The first is a repulsive interaction between an H atom of HF and a near pair of H atoms of C4H4 ring. The second is the double pi-type H bond between two lone pairs on a F atom and a far pair of H atoms.     

Characteristic of structures and pi-hydrogen bond of dimers C2H4-nFn-HF (n=0,1,2)

By the counterpoise-correlated potential energy surface method (interaction energy optimization), five structures of the C(2)H(4-n)F(n)-HF (n = 0,1,2) dimers with all real frequencies have been obtained at MP2/aug-cc-pVDZ level. The influence of F substituent effect on the structure and pi-hydrogen bond of dimer has been discussed. For C(2)H(4-n)F(n)-HF (n = 1,2), the pi-hydrogen bonds are elongated comparing with that for C(2)H(4)-HF. For C(2)H(3)F-HF, g-C(2)H(2)F(2)-HF, cis-C(2)H(2)F(2)-HF, the pi-hydrogen bonds are further deformed. These changes (elongate, shift, and deformation) of pi-hydrogen bond mainly come from deformation of pi-electron cloud of C=C bond. The pi-electron cloud is pushed towards the one C atom, the pi H-bond shift also to the C direction. Since the two lobes of pi-electron cloud have deviated slightly from the molecular vertical plane passing through C=C bond, the pi-hydrogen bond is sloped. Intermolecular interaction energies of the dimers are calculated to be -3.9 for C(2)H(4)-HF, -2.8 for C(2)H(3)F-HF, -2.1 for g-C(2)H(2)F(2)-HF, -1.6 for cis-C(2)H(2)F(2)-HF, -1.3 kcal/mol for trans-C(2)H(2)F(2)-HF, at CCSD(T)/aug-cc-pVDZ level.     

Density functional study of the sigma and pi bond activation at the Pd=X (X = Sn, Si, C) bonds of the (H2PC2H4PH2)Pd=XH2 complexes. Is the bond cleavage homolytic or heterolytic?

The mechanism for the activation of the sigma bonds, the O-H of H2O, C-H of CH4, and the H-H of H2, and the pi bonds, the C[triple bond]C of C2H2, C=C of C2H4, and the C=O of HCHO, at the Pd=X (X = Sn, Si, C) bonds of the model complexes (H2PC2H4PH2)Pd=XH2 5 has been theoretically investigated using a density functional method (B3LYP). The reaction is significantly affected by the electronic nature of the Pd=X bond, and the mechanism is changed depending on the atom X. The activation of the O-H bond with the lone pair electron is heterolytic at the Pd=X (X = Sn, Si) bonds, while it is homolytic at the Pd=C bond. The C-H and H-H bonds without the lone pair electron are also heterolytically activated at the Pd=X bonds independent of the atom X, where the hydrogen is extracted as a proton by the Pd atom in the case of X = Sn, Si and by the C atom in the case of X=C because the nucleophile is switched between the Pd and X atoms depending on the atom X. In contrast, the pi bond activation of C[triple bond]C and C=C at the Pd=Sn bond proceeds homolytically, and is accompanied by the rotation of the (H2PC2H4PH2)Pd group around the Pd-Sn axis to successfully complete the reaction by both the electron donation from the pi orbital to Sn p orbital and the back-donation from the Pd dpi orbital to the pi orbital. On the other hand, the activation of the C=O pi bond with the lone pair electron at the Pd=Sn bond has two reaction pathways: one is homolytic with the rotation of the (H2PC2H4PH2)Pd group and the other is heterolytic without the rotation. The role of the ligands controlling the activation mechanism, which is heterolytic or homolytic, is discussed.     

Theoretical study on intermolecular interactions between furan and dihalogen molecules XY(X,Y=F,Cl,Br)

Equilibrium geometries, interaction energies, atomic charge, and charge transfer for the intermolecular interactions between furan and dihalogen molecules XY(X; Y=F,Cl,Br) were studied at the MP2aug-cc-pVDZ level. Three types of geometry are observed in these interactions: the pi-type geometry (I), in which the XY lies above the furan ring and almost perpendicularly to the C4-C5 bond of furan; the sigma-type geometry (II), where the X atom is pointed toward the nonbonding electron pair (n pair) of oxygen atom in furan; and the chi-type geometry (III), describing a blueshift hydrogen bond formed between the hydrogen atom of furan and dihalogen molecules XY. The calculated interaction energies show that the pi-type structures are more stable than the corresponding sigma-type and chi-type structures. To study the nature of the intermolecular interactions, an energy decomposition analysis was carried out and the results indicate that both the pi-type and sigma-type interactions are dominantly inductive energy in nature, while dispersion energy governs the chi-type interactions.     

Synthesis and Crystal Structure of Tris(N-p- methylphenyl-3-hydroxy- 2-ethyl-4-pyridinonato)iron(III)

1 INTRODUCTION A number of hydroxypyrones and hydroxypyridinones are being assessed or considered as orally effective chelators for treatment iron or aluminum overload[1,2]. Almost all present and potential applications involve the tris-ligand complexes of metal(III) cations, as for example in administration of iron(III) complexes for the treatment of anaemia[3], and the appropriate isotopes (e.g. 67Ga, 111In, 90Y) for radiotherapy or the isotopes of gadolinium for magnetic resonance …     

Observation of the pi...H hydrogen-bonded ternary complex, (C(2)H(4))(2)H(2)O, using matrix isolation infrared spectroscopy

FTIR absorption spectra of water-containing ethene:Ar matrices, with compositions of ethene up to 1:10 ethene:Ar, have been recorded. Systematically increasing the concentration of ethene reveals features in the spectra consistent with the known 1:1 ethene:water complex, which subsequently disappear on further increase in ethene concentration. At high concentrations of ethene, new features are observed at 3669 and 3585 cm(-1), which are red-shifted with respect to matrix-isolated nu(3) and nu(1) O-H stretching modes of water and the 1:1 ethene:water complex. These shifts are consistent with a pi...H interaction of a 2:1 ethene:water complex of the form (C(2)H(4)...H-O-H...C(2)H(4)). The analogous (C(2)D(4))(2)H(2)O complex shows little shifting from positions associated with (C(2)H(4))(2)H(2)O, while the (C(2)H(4))(2)D(2)O isotopomer shows large shifts to 2722.3 and 2617.2 cm(-1), having identical nu(3)(H(2)O)/nu(3)(D(2)O) and nu(1)(H(2)O)/nu(1)(D(2)O) values when compared with monomeric water isotopomers. Features at 3626.1 and 2666.2 cm(-1) are also observed and are attributed to (C(2)H(4))(2)HDO. DFT calculations at the B3LYP/6-311+G(d,p) level for each isotopomer are presented, and the predicted vibrational frequencies are directly compared with experimental values. The interaction energy for the formation of the 2:1 ethene:water complex from the 1:1 ethene:water complex is also presented.     

Study of pi halogen bonds in complexes C2H(4-n)Fn-ClF (n = 0-2)

The pi-halogen bond may be considered, in a broad sense, essentially a pi-hydrogen bond. Using the counterpoise-corrected potential energy surface method (interaction energy optimization), the stationary structures of the C2H(4-n)Fn-ClF (n = 0-2) complexes with all real frequencies have been obtained at the MP2/aug-cc-pVDZ level. For C2H(4-n)Fn-ClF (n = 0-2), the pi-halogen bond has a long distance and is elongated by the F substituent effect. The pi-halogen bond length order is 2.661 A for C2H4-ClF < 2.745 A for C2H3F-ClF < 2.766 A for g-C2H2F2-ClF < 2.8076 A for trans-C2H2F2-ClF < 2.8079 A for cis-C2H2F2-ClF. For three complexes C2H3F-ClF, g-C2H2F2-ClF, and cis-C2H2F2-ClF, the pi-halogen bonds are further shifted and sloped by the F substituent effect. The F substituent effect reduces also the interaction energy of the pi-halogen bond. The interaction energies are respectively -3.7 for C2H4-ClF, -2.8 for C2H3F-ClF, -2.3 for g-C2H2F2-ClF, -1.9 for cis-C2H2F2-ClF, and -1.8 kcal/mol for trans-C2H2F2-ClF, at the CCSD(T)/aug-cc-pVDZ level. The electron correlation contribution of the interaction energy is large for C2H(4-n)Fn-ClF (n = 0-2), which shows that the stabilities of the pi-halogen bond systems results primarily from the dispersion interaction. In the double F substituent systems, the interaction energy of the pi-halogen bond structure with a longer interaction distance is larger than that of the corresponding pi-hydrogen bond structure with a shorter interaction distance. This may be because there are the large electron correlation contributions of the interaction energy, and a secondary interaction between lone pairs of Cl atom and some atoms (H, C) with positive charges in the pi-halogen bond structure.     

C(4)N(3)OH(7).Zn(H2O)HPO4, a neutral zincophosphate cluster

C(4)N(3)OH(7).Zn(H(2)O)HPO(4), built up from 4-rings of ZnO(2)(H(2)O)N and HPO(4) tetrahedra, is the first neutral, molecular, zincophosphate cluster. The unit-cell packing involves numerous O-H...O and N-H...O hydrogen bonds and pi...pi stacking interactions. Crystal data: C(4)N(3)OH(7).Zn(H(2)O)HPO(4), M(r) = 292.49, triclinic, P1 (No. 2), a = 9.2956(5) A, b = 11.2077(6) A, c = 19.8319(12) A, alpha = 80.314(1) degrees, beta = 78.829(1) degrees, gamma = 89.241(1) degrees, V = 1997.7(2) A(3), Z = 4.     

Structures of 1-(arylseleninyl)naphthalenes: O, G, and Y dependences in 8-G-1-[p-YC6H4Se(O)]C10H6

Structures of 8-G-1-[p-YC6H4Se(O)]C10H6 [1 (G = H), 2 (G = F), 3 (G = Cl), and 4 (G = Br): Y = H, OMe, OCH2Ph, t-Bu, Me, Cl, and NO2] and (1-C10H7)2SeO (5) are investigated by the X-ray crystallographic analysis. Structures of 1 are all A with regard to the naphthyl group (1 (A)), where the Se-C(Ar) and Se-O bonds are perpendicular to and parallel to the naphthyl plane, respectively. Those of 2-4 are also A. Since structures of 8-G-1-(p-YC6H4Se)C10H6 [7 (G = F), 8 (G = Cl), and 9 (G = Br)] are all B, the results exhibit that B of 7-9 change dramatically to A of 2-4 with the introduction of O atoms. The factor to determine the A structures of 1-4 by O is called O dependence. The origin of the O dependence is the nonbonded np(O)- - -pi(Nap) interaction, which results in CT from np(O) to pi(Nap) since O in 1-4 is highly electron rich due to the polar Se+=O- bond and pi(Nap) acts as an acceptor. There are two types of np(O)'s, npy(O) and npz(O), if the directions of the Se-O bond and the p-orbitals of pi(Nap) are taken in the x- and z-axes, respectively. Double but independent np(O)- - -pi(Nap) interactions in 5 lead to 5 (AA). The conformation of the p-YC6H4Se group in 1 changes depending on Y (Y dependence), although the effect is not strong. The Y dependence is explained on the basis of the magnitude of CT of the np(O)-->pi(Ar) type in 1, in addition to the np(O)- - -pi(Nap) interaction. The structure around the Se=O group in 1 is close to that of 5 (AA), if the accepting ability of the p-YC6H4Se group is similar to that of the naphthyl group. A of 2-4 are further stabilized by the np(G)- - -sigma(Se-O) 3c-4e interactions, which are called G dependence. QC calculations performed on the methyl analogues of 1-4 (11-14, respectively) reproduced the observed structures, supported the above discussion, and revealed the energy profiles. The energy-lowering effect of the O dependence would be close to the G dependence of the nonbonded n(Br)- - -sigma(Se-O) 3c-4e interaction in 14 if the steric repulsion between Br and Se is contained in the G dependence. The value is roughly predicted as 20 kJ mol(-1). The structures of 1-5 are well explained by O, G, and Y dependences.     

5-苯基-3,5-二乙氧基-2(5H)-呋喃酮的晶体结构

标题化合物C14H16O4的晶体结构用X-射线单晶衍射法测定。晶体属三斜晶系,P空间群,晶胞参数a =8.696(2), b=8.943(2) , c=9.379(2) ?, ( = 69.28(3), ( =76.67(3), ( =80.28(3)o, V=660.8(3) ? 3, Z=2, Mr=248.28, Dx=1.248 g/cm3, F(000)=264, μ(MoK()=0.0851 mm—1。晶体结构用直接法解出,经全矩阵最小二乘法对原子参数进行修正,最终的偏离因子为R=0.061, wR=0.089。标题化合物有2个环：呋喃酮环和苯环。由C(1),C(2),C(3),C(4),O(4)构成的五元呋喃酮环的5个原子较好地处于1个平面上,平均偏差为0.0078?。O(2),O(3) 两个原子与呋喃酮环共平面。呋喃酮环和苯环之间的两面角为79.39o。     

Electronic properties of hydrogen-bonded complexes of benzene(HCN)(1-4): comparison with benzene(H2O)(1-4)

The electronic properties, specifically, the dipole and quadrupole moments and the ionization energies of benzene (Bz) and hydrogen cyanide (HCN), and the respective binding energies, of complexes of Bz(HCN)(1-4), have been studied through MP2 and OVGF calculations. The results are compared with the properties of benzene-water complexes, Bz(H(2)O)(1-4), with the purpose of analyzing the electronic properties of microsolvated benzene, with respect to the strength of the CH/π and OH/π hydrogen-bond (H-bond) interactions. The linear HCN chains have the singular ability to interact with the aromatic ring, preserving the symmetry of the latter. A blue shift of the first vertical ionization energies (IEs) of benzene is observed for the linear Bz(HCN)(1-4) clusters, which increases with the length of the chain. NBO analysis indicates that the increase of the IE with the number of HCN molecules is related to a strengthening of the CH/π H-bond, driven by cooperative effects, increasing the acidity of the hydrogen cyanide H atom involved in the π H-bond. The longer HCN chains (n ≥ 3), however, can bend to form CH/N H-bonds with the Bz H atoms. These cyclic structures are found to be slightly more stable than their linear counterparts. For the nonlinear Bz(HCN)(3-4) and Bz(H(2)O)(2-4) complexes, an increase of the binding energy with the number of solvent molecules and a decrease of the IE of benzene, relative to the values for the Bz(HCN) and Bz(H(2)O) complexes, respectively, are observed. Although a strengthening of the CH/π and OH/π H-bonds, with increasing n, also takes place for the Bz(H(2)O)(2-4) and Bz(HCN)(3-4) nonlinear complexes, Bz proton donor, CH/O, and CH/N interactions are at the origin of this decrease. Thus CH/π and OH/π H-bonds lead to higher IEs of Bz, whereas the weaker CH/N and CH/O H-bond interactions have the opposite effect. The present results emphasize the importance of both aromatic XH/π (X = C, O) and CH/X (X = N, O) interactions for understanding the structure and electronic properties of Bz(HCN)(n) and Bz(H(2)O)(n) complexes.     

Ferromagnetism in malonato-bridged copper(II) complexes. Synthesis,crystal structures,and magnetic properties of [[Cu(H2O)3][Cu(mal)2(H2O)]]n and [[Cu(H2O)4]2[Cu(mal)2(H2O)]][Cu(mal)2(H2O)2][[Cu(H2O)4][Cu(mal)2(H2O)2][(H2mal = malonic acid)

Three malonato-bridged copper(II) complexes of the formulas [[Cu(H2O)3][Cu(C3H2O4)2(H2O)]]n (1), [[Cu(H2O)4]2[Cu(C3H2O4)2(H2O)]] [Cu(C3H2O4)2(H2O)2][[Cu(H2O)4][Cu(C3H2O4)2(H2O)2]] (2), and [Cu(H2O)4][Cu(C3H2O4)2(H2O)2] (3) (C3H2O4 = malonate dianion) have been prepared, and the structures of the two former have been solved by X-ray diffraction methods. The structure of compound 3 was already known. Complex 1 crystallizes in the orthorhombic space group Pcab, Z = 8, with unit cell parameters of a = 10.339(1) A, b = 13.222(2) A, and c = 17.394(4) A. Complex 2 crystallizes in the monoclinic space group P2/c, Z = 4, with unit cell parameters of a = 21.100(4) A, b = 21.088(4) A, c = 14.007(2) A, and beta = 115.93(2) degrees. Complex 1 is a chain compound with a regular alternation of aquabis(malonato)copper(II) and triaquacopper(II) units developing along the z axis. The aquabis(malonato)copper(II) unit acts as a bridging ligand through two slightly different trans-carboxylato groups exhibiting an anti-syn coordination mode. The four carboxylate oxygens, in the basal plane, and the one water molecule, in the apical position, describe a distorted square pyramid around Cu1, whereas the same metal surroundings are observed around Cu2 but with three water molecules and one carboxylate oxygen building the equatorial plane and a carboxylate oxygen from another malonato filling the apical site. Complex 2 is made up of discrete mono-, di-, and trinuclear copper(II) complexes of the formulas [Cu(C3H2O4)2(H2O)2]2-, [[Cu(H2O)4] [Cu(C3H2O4)2(H2O)2]], and [[Cu(H2O)4]2[Cu(C3H2O4)2(H2O)]]2+, respectively, which coexist in a single crystal. The copper environment in the mononuclear unit is that of an elongated octahedron with four carboxylate oxygens building the equatorial plane and two water molecules assuming the axial positions. The neutral dinuclear unit contains two types of copper atoms, one that is six-coordinated, as in the mononuclear entity, and another that is distorted square pyramidal with four water molecules building the basal plane and a carboxylate oxygen in the apical position. The overall structure of this dinuclear entity is nearly identical to that of compound 3. Finally, the cationic trimer consists of an aquabis(malonato)copper(II) complex that acts as a bismonodentate ligand through two cis-carboxylato groups (anti-syn coordination mode) toward two tetraaqua-copper(II) terminal units. The environment of the copper atoms is distorted square pyramidal with four carboxylate oxygens (four water molecules) building the basal plane of the central (terminal) copper atom and a water molecule (a carboxylate oxygen) filling the axial position. The magnetic properties of 1-3 have been investigated in the temperature range 1.9-290 K. Overall, ferromagnetic behavior is observed in the three cases: two weak, alternating intrachain ferromagnetic interactions (J = 3.0 cm-1 and alpha J = 1.9 cm-1 with H = -J sigma i[S2i.S2i-1 + alpha S2i.S2i+1]) occur in 1, whereas the magnetic behavior of 2 is the sum of a magnetically isolated spin doublet and ferromagnetically coupled di- (J3 = 1.8 cm-1 from the magnetic study of the model complex 3) and trinuclear (J = 1.2 cm-1 with H = -J (S1.S2 + S1.S3) copper(II) units. The exchange pathway that accounts for the ferromagnetic coupling, through an anti-syn carboxylato bridge, is discussed in the light of the available magneto-structural data.     

The molecular and crystal structure of tert-butyl Nalpha-tert-butoxycarbonyl-L-(S-trityl)cysteinate and the conformation-stabilizing function of weak intermolecular bonding

The title compound, C31H37NO4S [systematic name: (R)-tert-butyl-2-[(tert-butoxycarbonyl)amino]-3-(tritylsulfanyl)propanoate] is an L-cysteine derivative with three functions: NH2, COOH and SH, blocked by protecting groups tert-butoxycarbonyl, tert-butyl and trityl, respectively. The main chain of the molecule adopts the extended, nearly all-trans C5 conformation with the intramolecular N-H...O=C hydrogen bond. The urethane group is not involved in any intermolecular hydrogen bonding. Only weak intermolecular hydrogen bonds and hydrophobic contacts are observed in the crystal structure. These are C-H...O hydrogen bonds and CH/pi interactions with donor...acceptor distances, C...O ca. 3.5 A and C...C ca. 3.7 A, respectively. The first type of interaction links phenyl H-atoms and carbonyl groups. The second type of interaction is formed between a methyl group of the tert-butyl fragment and a trityl phenyl ring. The resulting molecular conformation in the crystal is very close to an ab initio minimum energy conformer of the isolated molecule. The extended C5 conformation of the main peptide chain is the same and there is slight discrepancy in the disposition of trityl phenyl rings. Their small dislocation creates the possibility of forming the entire network above of extensive, specific, weak intermolecular interactions; these constrain the molecule and permit it to retain the minimum energy C5 conformation of its main chain in the solid state. In contrast, in n-hexane solution, where such specific interactions cannot occur, only a small population of the molecules adopts the extended C5 conformation.     

Synthesis and characterization of (R-C5H14N2)2[Ga4(C2O4)(H2PO4)2(PO4)4].2H2O, a layered gallium phosphatooxalate containing a chiral amine

The first metal phosphatooxalate containing a chiral amine, (R-C5H14N2)2[Ga4(C2O4)(H2PO4)2(PO4)4].2H2O, has been synthesized hydrothermally and characterized by single-crystal X-ray diffraction and 31P MAS NMR spectroscopy. It crystallizes in the monoclinic space group P2(1) (No. 4) with a = 8.0248(4) A, b = 25.955(1) A, c = 9.0127(5) A, beta = 100.151(1) degrees, and Z = 2. The structure consists of GaO6 octahedra and GaO4 tetrahedra connected by coordinating C2O4(2-) and phosphate anions to form anionic sheets in the ac plane with charge-compensating diprotonated R-2-methylpiperazinium cations and water molecules between the layers. There is a good correlation between the NMR spectrum and the structure.     

Synthesis and Crystal Structure of 2-(4''-Methylphenoxy)-5,8,9-trimethyl-3-phenyl Thieno[3'',2'':5,6]pyrido[4,3-d]pyrimidin-4-(3H)-one Hydrochloride

The title compound 2-(4′-methylphenoxy)-5,8,9-trimethyl-3-phenyl thieno[3′,2′:5,6]pyrido[4,3-d]pyrimidin-4(3H)-one hydrochloride (C26H23Cl4N3O2S, Mr = 583.33) has been deter- mined by single-crystal X-ray diffraction. The crystal belongs to monoclinic, space group P21/c with a = 14.8442(11), b = 11.5131(8), c = 17.2010(13) (A), β = 113.7250(10)o, V = 2691.3(3) (A)3, Z = 4, Dc = 1.440 g/cm3, S = 1.094, μ = 0.547 mm-1, F(000) = 1200, the final R = 0.0571 and wR = 0.1458. X-ray analysis reveals that the title compound combines with a molecule of dichloromethane by an intramolecular hydrogen bond. The thienopyridine ring is almost coplanar, and the dihedral angle between the thiophene plane and the pyridine plane is 0.6o.     

Raman,infrared and force field studies of K2(12)C2O4 x H2O and K2(13)C2O4 x H2O in the solid state and in aqueous solution,and of (NH4)2(12)C2O4 x H2O and (NH4)2(13)C2O4 x H2O in the solid state

The Raman and infrared spectra of solid K2(12)C2O4 x H2O are reported together with, for the first time, the corresponding Raman and infrared spectra of solid K2(13)C2O4 x H2O. Raman spectra of aqueous solutions of both isotopomers are also reported. In the solid state the oxalate anion is planar with D2h symmetry in this salt, whereas in aqueous solution the Raman spectra of the anion are best interpreted on the basis of D2d symmetry. The Raman spectra of solid (NH4)2(12)C2O4 x H2O and (NH4)2(13)C2O4 x H2O, in which the oxalate anion is twisted from planarity by 28 degrees about the CC bond, have also been recorded. Several reassignments have been made. The harmonic force field for the oxalate anion in the D2h, D2 and D2d geometries has been determined in part, and approximate values of key valence force constants determined. All the observed band wavenumbers and 12C/13C isotopic shifts are well reproduced by the force fields. The potential energy distribution of the totally symmetric normal modes of planar oxalate indicates that each mode consists of extensively mixed symmetry corrdinates and that the labels previously used for the bands seen here at 475 and 879 cm(-1) would better be described as v(CC) and deltaS(CO2), respectively, putting them in the same wavenumber order as v(NN) and deltaS(NO2) for the isoelectronic and isostructural molecule N2O4. The stretching force constants of N2O4 and planar C2O4(2-) are established to be in the order f(NN) < f(CC) and f(NO) > f(CO), consistent with the known relative bond lengths.     

Diplatinum alkynyl chromophores as sensitisers for lanthanide luminescence in Pt2Ln2 and Pt2Ln4 (Ln = Eu, Nd, Yb) arrays with acetylide-functionalized bipyridine/phenanthroline

Incorporation of diplatinum complex Pt2(micro-dppm)2(bpyC[triple bond]C)4 or Pt2(mu-dppm)2(phenC[triple bond]C)4 with Ln(hfac)3(H2O)2 (Ln = Nd, Eu, Yb) gave a series of Pt2Ln2 and Pt2Ln4 bimetallic arrays, in which the excitation of d(Pt) -->pi*(R-C[triple bond]C) MLCT absorption induces sensitisation of lanthanide luminescence through efficient d --> f energy transfer from Pt(II) alkynyl chromophores.     

A hydrothermal investigation of the 1/2V2O5-H2C2O4/H3PO4/NH4OH system: synthesis and structures of (NH4)VOPO(4).1.5H2O, (NH4)0.5VOPO(4).1.5H2O, (NH4)2[VO(H2O)3]2[VO(H2O)][VO(PO4)2](2).3H2O, and (NH4)2[VO(HPO4)]2(C2O4).5H2O

The 1/2V2O5-H2C2O4/H3PO4/NH4OH system was investigated using hydrothermal techniques. Four new phases, (NH4)VOPO(4).1.5H2O (1), (NH4)0.5VOPO(4).1.5H2O (2), (NH4)2[VO(H2O)3]2[VO(H2O)][VO(PO4)2]2.3H2O (3), and (NH4)2[VO(HPO4)]2(C2O4).H2O (4), have been prepared and structurally characterized. Compounds 1 and 2 have layered structures closely related to VOPO(4).2H2O and A0.5VOPO4.yH2O (A = mono- or divalent metals), whereas 3 has a 3D open-framework structure. Compound 4 has a layered structure and contains both oxalate and phosphate anions coordinated to vanadium cations. Crystal data: (NH4)VOPO(4).1.5H2O, tetragonal (I), space group I4/mmm (No. 139), a = 6.3160(5) A, c = 13.540(2) A, Z = 4; (NH4)0.5VOPO(4).1.5H2O, monoclinic, space group P2(1)/m (No. 11), a = 6.9669(6) A, b = 17.663(2) A, c = 8.9304(8) A, beta = 105.347(1) degrees, Z = 8; (NH4)2[VO(H2O)3]2[VO(H2O)][VO(PO4)2]2.3H2O, triclinic, space group P1 (No. 2), a = 10.2523(9) A, b = 12.263(1) A, c = 12.362(1) A, alpha = 69.041(2) degrees, beta = 65.653(2) degrees, gamma = 87.789(2) degrees, Z = 2; (NH4)2[VO(HPO4)]2(C2O4).5H2O, monoclinic (C), space group C2/m (No. 12), a = 17.735(2) A, b = 6.4180(6) A, c = 22.839(2) A, beta = 102.017(2) degrees, Z = 6.     

From weak interactions to covalent bonds: a continuum in the complexes of 1,8-bis(dimethylamino)naphthalene

Experimental charge density distributions in a series of ionic complexes of 1,8-bis(dimethylamino)naphthalene (DMAN) with four different acids: 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid), 4,5-dichlorophthalic acid, dicyanoimidazole, and o-benzoic sulfimide dihydrate (saccharin) have been analyzed. Variation of charge density properties and derived local energy densities are investigated, over all inter- and intramolecular interactions present in altogether five complexes of DMAN. All the interactions studied [[O...H...O](-), C[bond]H...O, [N[bond]H...N](+), O[bond]H...O, C[bond]H...N, C pi...N pi, C pi...C pi, C[bond]H...Cl, N[bond]H(+)] follow exponential dependences of the electron density, local kinetic and potential energies at the bond critical points on the length of the interaction line. The local potential energy density at the bond critical points has a near-linear relationship to the electron density. There is also a Morse-like dependence of the laplacian of rho on the length of interaction line, which allows a differentiation of ionic and covalent bond characters. The strength of the interactions studied varies systematically with the relative penetration of the critical points into the van der Waals spheres of the donor and acceptor atoms, as well as on the interpenetration of the van der Waals spheres themselves. The strong, charge supported hydrogen bond in the DMANH(+) cation in each complex has a multicenter character involving a [[Me(2)N[bond]H....NMe(2)](+)....X(delta-)] assembly, where X is the nearest electronegative atom in the crystal lattice.