DFT Study on a Heterofullerene C_(58)Sn with Odd Number of Atoms

Density functional theory calculations and structural minimization techniques have been employed to characterize the structural and electronic properties of [5,6]-heterofullerene-C58Sn-C2. Since the heterofullerene molecule CssSn has a nearly planar tetra-coordinated Sn atom on the skeleton of cage, it is a heterofullerene molecule with odd number of atoms and a novel molecule. Vibrational frequencies of the molecule have been calculated at the B3LYP/CEP-31G level of theory. The absence of imaginary vibrational frequency confirms that the molecule corresponds to a true minimum on the potential energy hypersurface, and its heat of formation was estimated in this study. Owing to the C2 symmetry of [5,6]-heterofullerene-C58Sn-C2, it is a chiral molecule.     

An enormous vibrational motion: the gas-phase structure of dimethyl-bis(methoxyethynyl) germanium

The structure of dimethyl-bis(methoxyethynyl) germanium has been determined in the gas phase by electron diffraction utilising flexible restraints from quantum chemical calculations. Theoretical methods (B3LYP/6-311+G* and MP2/6-311+G*) predict a low barrier to rotation of the methoxy groups in the molecule in addition to low-frequency vibrations of the long ethynyl chains. In the equilibrium structure the Ge-C[triple bond]C angles of the two methoxyethynyl fragments in the molecule are computed to deviate by up to 4 degrees from the linear arrangement. As a consequence of low-frequency large-amplitude vibrational motion the experimental structure of these fragments without applying vibrational corrections deviates considerably from linearity, while the structure corrected for vibrational effects using the harmonic approximation and taking into account a non-linear transformation between internal and Cartesian coordinates (r(h1)) shows closer agreement with theory. The main experimental structural parameters of dimethyl-bis(methoxyethynyl) germanium (r(h1)) are: r(Ge-C)(mean), 192.5(1) pm; DeltaGeC =r(Ge-C(methyl))-r(Ge-C(ethynyl)), 4.5(5) pm, r(C[triple bond]C)(mean), 122.8(2) pm; r(C-O)(mean), 138.9(3) pm; DeltaCO =r(C(methyl)-O)-r(C(ethynyl)-O), 14.5(2) pm, r(C-H)(mean), 109.1(4) pm; [angle](X-C-H)(mean)(X = Ge,O), 109(1) degree; [angle]C(ethynyl)-Ge-C(ethynyl), 108.1(4) degree; [angle]C(methyl)-Ge-C(methyl), 113.4(5) degree; [angle]Ge-C[triple bond]C, 163(1) degree; [angle]C[triple bond]C-O, 176(2) degree; [angle]C-O-C, 115.2(6) degree; methoxy group torsion, tau, 36(9) degree from the position in which the C-O bond eclipses the further Ge-C(ethynyl) bond.     

Heterodimetallic germanium(IV) complex structures with transition metals

The hydrothermal synthesis and structural characterization of a number of complex compounds containing the divalent tris(oxalato-O,O')germanate anion, [Ge(C2O4)3]2-, or the neutral bis(oxalate-O,O')germanium fragment, [Ge(C2O4)2], with transition-metal (M) cationic complexes of 1,10'-phenanthroline (phen) is reported: [M(phen)3][Ge(C2O4)3].xH2O [where M2+ = Cu2+ (1a and 1b), Fe2+ (2a and 2b), Ni2+ (3), Co2+ (4); x = 0.2 for 2b], [MGe(phen)2(mu2-OH)2(C2O4)2] [where M2+ = Cd2+ (5) and Cu2+ (6)]. The isolation of two polymorphs with Cu2+ (1a and 1b) and other pseudo-polymorphs for Fe2+ (2a and 2b) was rationalized based on slightly different molar ratios for the starting materials. All compounds have been characterized using EDS, SEM, vibrational spectroscopy (FT-IR and FT-Raman), thermogravimetry, and CHN elemental composition and their structure determined on the basis of single-crystal X-ray diffraction studies. The crystal packing of the different chemical moieties for each series of compounds was discussed on the basis of the various intermolecular interactions present (strong C-H...pi and weak C-H...O hydrogen-bonding interactions, C-H...pi and pi-pi contacts).     

Competition and selectivity in the reaction of nitriles on ge(100)-2x1

We have experimentally investigated bonding of the nitrile functional group (R-Ctbd1;N:) on the Ge(100)-2x1 surface with multiple internal reflection infrared spectroscopy. Density functional theory calculations are used to help explain trends in the data. Several probe molecules, including acetonitrile, 2-propenenitrile, 3-butenenitrile, and 4-pentenenitrile, were studied to elucidate the factors controlling selectivity and competition on this surface. It is found that acetonitrile does not react on the Ge(100)-2x1 surface at room temperature, a result that can be understood with thermodynamic and kinetic arguments. A [4+2] cycloaddition product through the conjugated pi system and a [2+2] C=C cycloaddition product through the alkene are found to be the dominant surface adducts for the multifunctional molecule 2-propenenitrile. These two surface products are evidenced, respectively, by an extremely intense nu(C=C=N), or ketenimine stretch, at 1954 cm(-)(1) and the nu(Ctbd1;N) stretch near 2210 cm(-)(1). While the non-conjugated molecules 3-butenenitrile and 4-pentenenitrile are not expected to form a [4+2] cycloaddition product, both show vibrational modes near 1954 cm(-)(1). Additional investigation suggests that 3-butenenitrile can isomerize to 2-butenenitrile, a conjugated nitrile, before introduction into the vacuum chamber, explaining the presence of the vibrational modes near 1954 cm(-)(1). Pathways directly involving only the nitrile functional group are thermodynamically unfavorable at room temperature on Ge(100)-2x1, demonstrating that this functional group may prove useful as a vacuum-compatible protecting group.     

Synthesis and structures of an unusual germanium(II) calix[4]arene complex and the first germanium(II) calix[8]arene complex and their reactivity with diiron nonacarbonyl

The protonolysis reaction of the germanium(II) amide Ge[N(SiMe3)2]2 with calix[4]arene and calix[8]arene furnishes the two germanium(II) calixarene complexes {calix[4]}Ge2 and {calix[8]}Ge4, respectively, which have been crystallographically characterized. The calix[4]arene complex contains a Ge2O2 rhombus at the center of the molecule and is one of the only four germanium(II) calix[4]arenes that have been structurally characterized. The calix[8]arene species is the first reported germanium calix[8]arene complex, and it exhibits an overall bowl-shaped structure which contains two Ge2O2 fragments. The latter complex reacts with Fe2(CO)9 to yield an octairon compound, which has also been structurally characterized and contains four GeFe2 triangles arranged around the macrocyclic ring. The germanium(II) centers are oxidized to germanium(IV) in this process, with concomitant reduction of the neutral diiron species to Fe2(CO)(8)2- anions.     

Experimental and theoretical investigation of the molecular and electronic structure of anticancer drug camptothecin

The Fourier Transform Infrared spectrum of (S)-4 ethyl-4-hydroxy-1H-pyrano [3',4':6,7]-indolizino-[1,2-b-quinoline-3,14-(4H,12H)-dione] [camptothecin] was recorded in the region 4000-400 cm(-1). The Fourier Transform Raman spectrum of camptothecin (CPT) was also recorded in the region 3500-50 cm(-1). Quantum chemical calculations of geometrical structural parameters and vibrational frequencies of CPT were carried out by MP2/6-31G(d,p) and density functional theory DFT/B3LYP/6-311++G(d,p) methods. The assignment of each normal mode has been made using the observed and calculated frequencies, their IR and Raman intensities. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FT-IR and FT-Raman spectra. Most of the computed frequencies were found to be in good agreement with the experimental observations. The isotropic chemical shifts computed by (13)C and (1)H NMR analysis also show good agreement with experimental observations. Comparison of calculated spectra with the experimental spectra provides important information about the ability of computational method to describe the vibrational modes of large sized organic molecule.     

Synthesis, Crystal Structure and Thermal Stability of a Nickel（Ⅱ） Complex with Bicycle[2.2.1]-2-hepten-5,6-dicarboxylic Acid

The nickel complex {Ni(2,2-bipy)(H2O)3[C8H11O2(COO)]}(H2O)3 with bicycle-[2.2.1]-2-hepten-5,6-dicarboxylic acid [C7H8(COOH)2] and 2,2'-bipyridine (bipy) as ligands has been synthesized and characterized. It crystallizes in monoclinic, space group P , with a = 0.74975(3), b = 1.20309(4), c = 1.30593(4) nm, α = 109.861(2), β = 98.519(2), γ = 90.575(2)o, V = 1.09337(7) nm3, Dc = 1.552 g/cm3, Z = 2, F(000) = 524, the final GOOF = 1.064, R = 0.0397 and wR = 0.1171. The crystal structure shows that the nickel ion is coordinated with four oxygen atoms from one bicycle[2.2.1]-2-hepten-5,6-dicarboxylic acid molecule and three water molecules and two nitrogen atoms from the 2,2′-bipyridine molecule, forming a distorted octahedral coordination geometry. The result of TG analysis shows that the title complex is stable under 200.0 ℃.     

Raman spectroscopic analysis of GeS2-Ga2S3-PbI2 chalcohalide glasses

The structures of pseudo-binary GeS2-PbI2, Ga2S3(GaS)-PbI2 and pseudo-ternary GeS2-Ga2S3-PbI2 chalcohalide systems were investigated by Raman scattering spectroscopy. By evolving the vibrational bands as a function of PbI2 content, it was verified that the effect of addition of PbI2 to the glass network is threefold, namely: (i) the conversion of GeS4 tetrahedra to GeS3I and GeS2I2 structural units, (ii) the destruction of ethane-like S3Ga(Ge)-(Ge)GaS3 structural units and formation of GaS3I and GeS3I ones and (iii) formation of short S-S chains and [PbIn] structural units when the concentration of PbI2 is high.     

双环[2.2.1]-2-庚烯-5，6-二甲酸镍配合物的合成、晶体结构及热稳定性

The nickel complex Ni(phen)(H₂O)₃[C₈H₁₁O₂(COO)] has been synthesized with bicycle[2.2.1]hept-2-en-5,6-dicarboxylic acid [C₇H₈(COOH)₂] by means of solvent way. It crystallizes in the triclinic space group P1, with a=0.780 58(16) nm, b=1.189 9(2) nm, c=1.214 8(2) nm, α=66.20(3)°, β=88.28(3)°, γ=86.33(3)°, V=1.030 3(4) nm³, D_c=1.554 g·cm^-3, Z=2, F(000)=502. Final GOF=1.107, R₁=0.026 4, wR₂=0.070 2. The crystal structure shows that the nickel ion is coordinated with four oxygen atoms from one bicycle[2.2.1]-2-hepten-5,6-dicarboxylic acid molecule and three water molecules, respectively, with two nitrogen atoms from the 1,10-phenanthroline molecule, forming a distorted octahedral coordination geometry. The result of TG analysis shows that the title complex was stable under 210.0 ℃. CCDC: 741933.     

Acidic properties of [Al], [Ga] and [Fe] isomorphously substituted zeolites. Density functional model cluster study of the complexes with a probe CO molecule

The Brønsted acid strength and related characteristics of bridging hydroxyl groups in [Al]-, [Ga]- and [Fe]-framework-substituted zeolites have been studied using a model cluster density functional approach based on a gradient-corrected exchange-correlation energy functional. The acidity is found to decrease in the order Al(OH)Si > Ga(OH)Si > Fe(OH)Si in agreement with existing experimental and theoretical results. The present quantification is based on the calculated deprotonation energy of H₃Si(OH)TH₃, on the adsorption energy of a CO probe molecule as well as on the changes of the vibrational frequencies and absolute IR intensities of the O---H and of the C---O modes induced by CO adsorption. The vibrational parameters of the carbonyl adsorption complex in [Fe]-zeolites are predicted.     

Reversible dimerization of [5,6]-C60O

The recently discovered [5,6]-open isomer of C(60)O has been found to undergo facile dimerization to form a new C(2) symmetry isomer of C(120)O(2), which can be photodissociated with relatively high efficiency to regenerate monomeric [5,6]-C(60)O. High yield dimerization of [5,6]-C(60)O proceeds spontaneously in toluene solution near room temperature. On the basis of (13)C NMR spectroscopy, ab initio quantum computations, and HPLC retention patterns, the resulting C(120)O(2) product has been deduced to be a nonpolar dimer of C(2) symmetry in which the C(60)O moieties are linked by two single bonds between sp(3)-hybridized carbon atoms adjacent to oxygen atoms. Photophysical properties of this dimer have also been measured and compared to those of C(120), the [2 + 2]-dimer of C(60). The ground-state absorption spectrum of C(120)O(2) in toluene is slightly red-shifted relative to that of C(120), with a distinctive peak at 329 nm and an S(1)-S(0) origin band at 704 nm. Its fluorescence spectrum shows two major peaks at 718 and 793 nm. In room-temperature toluene, the measured triplet state intrinsic lifetime of this C(120)O(2) isomer is 34 +/- 2 micros, a value somewhat shorter than that of C(120) (44 micros). C(120)O(2) undergoes photodissociation from its triplet state to regenerate monomeric [5,6]-C(60)O with quantum yields of 2.5% at 24 degrees C and 43% at 70 degrees C. It can therefore serve as a stable reactant for photolytic production of [5,6]-C(60)O. As a simple fullerene adduct that reacts under mild conditions, [5,6]-C(60)O may prove useful in special synthetic applications. Solutions of [5,6]-C(60)O are also unique because they can provide mixtures of a fullerene monomer and its dimer in a dynamic balance controllable by adjustment of concentration, temperature, and optical irradiation.     

Reflection–absorption IR and surface-enhanced IR spectroscopy of tetracarboethoxy t-butyl-calix[4]arene,as a host molecule with potential applications in sensor devices

A vibrational study of the calix[4]arene derivative 25,26,27,28-tetracarboethoxy-p-tert-butylcalix[4]arene (TCEC) is accomplished in this work. This characterization implies a study of its adsorption on metal (Cu and Ag) films by reflection–absorption IR spectroscopy (RAIRS) and surface-enhanced IR (SEIR) in transmission and reflection–absorption configurations. Metal surfaces for SEIR were obtained by a simple direct immobilization on Ge of Ag nanoparticles suspended in water. The goal of this research was an accurate vibrational characterization of the above calixarene molecule, paying special attention in the structural marker bands of ester groups, which play an important role in the molecular adsorption on such metals. The information derived from this study will serve to better understand the interaction of ester-functionalised calixarenes with these metals, in order to prepare sensor films with selective affinity towards polycyclic aromatic hydrocarbons (PAHs). The application of these surface techniques confirmed the importance of the ester groups in the immobilization and self-assembly of these host molecules to the metal surface and provided information about the orientation adopted by TCEC on the metal.     

Vibrational center-ligand couplings in transition metal complexes

The mode-tracking principle [J. Chem. Phys. 2003, 118, 1634] for the direct quantum chemical calculation of preselected, characteristic molecular vibrations makes vibrational analyses of very large molecules feasible. This is demonstrated here for the [(Ph(3)PAu)(6)C](2+) complex, in which 18 phenyl groups in the ligand sphere are explicitly taken into account. We are aiming at the motion of the endohedral carbon atom, which is in an extraordinary bonding situation because it is surrounded by an octahedral core of gold atoms in this cluster. Secondary effects of the full ligand sphere on the vibrations of the [Au(6)C] core embedded in [(R(3)PAu)(6)C](2+) clusters are investigated. For this purpose, local vibrations of the octahedral core are generated, and their long-range couplings with the phosphine ligand sphere become visible in the mode-tracking iterations. The exact normal modes of these characteristic vibrations of the cluster are then obtained after convergence of the mode-tracking refinement. This protocol allows us to assess the coupling of the outer ligand sphere with the inner core of the cluster in terms of changes of the vibrational frequencies and of the collective motions of the atomic nuclei. The vibrational frequencies of the octahedral [Au(6)C] core split due to symmetry breaking in the C(1)-symmetric [(Ph(3)PAu)(6)C](2+) cluster. Our study demonstrates how effects of the periphery of a large molecule on local vibrations can be quantified. Furthermore, we predict the first set of characteristic vibrational frequencies obtained with first-principles methods for this gold cluster, whose vibrational spectra have not yet been recorded experimentally.     

Vibrational frequencies and structural determination of triethynylmethylstannane

The normal mode frequencies and corresponding vibrational assignments of Triethynylmethylstannane (SnCH(3)(CCH)(3)) are examined theoretically using the Gaussian 98 set of quantum chemistry codes. Each of the vibrational modes was assigned to one of nine types of motion predicted by a group theoretical analysis (Sn-C stretch, C[triple bond]C stretch, C-H stretch, C[triple bond]C-H bend, Sn-C[triple bond]C bend, C-Sn-C bend, H-C-H bend, CH(3) wag, and CH(3) twist) utilizing the C(3v) symmetry of the molecule. A set of uniform scaling factors was derived for each type of motion. Predicted infrared and Raman intensities are reported.     

New pyrazolino- and pyrrolidino[60]fullerenes with transition-metal chelating pyridine substitutents: synthesis and complexation to Ru(II)

Three pyridine-substituted fullerene adducts, bis(2,2'-bipyridine)(2'-phenyl-5'-(2-pyridinyl)-2'H-[5,6]fullereno(C(60)-I(h))[1,9]pyrazole)ruthenium-bis(hexafluorophosphate) (1), bis(2,2'-bipyridine)(2'-phenyl-5'-(4-(4'-methyl-2,2'-bipyridinyl))-2'H-[5,6]fullereno(C(60)-I(h))[1,9]pyrazole)ruthenium-bis(hexafluorophosphate) (2), and bis(2,2'-bipyridine)(1',5'-dihydro-3'-methyl-2'-(4-(4'-methyl-2,2'-bipyridinyl))-2'H-[5,6]fullereno(C(60)-I(h))[1,9]pyrrole)ruthenium-bis(hexafluorophosphate) (3), have been prepared. The common features for these complexes are the short bridges between the fullerene and the pyridine moieties. [structure: see text]     

Vibrational frequencies and structural determination of diethynyldimethylsilane

The normal mode frequencies and corresponding vibrational assignments of diethynyldimethylsilane are examined theoretically using the Gaussian 98 set of quantum chemistry codes. Each of the vibrational modes was assigned to one of nine types of motion predicted by a group theoretical analysis (Si-C stretch, C[triple bond]C stretch, C-H stretch, C[triple bond]C-H bend, Si-C[triple bond]C bend, C-Si-C bend, H-C-H bend, CH3 wag, and CH3 twist) utilizing the C3v symmetry of the molecule. A set of uniform scaling factors was derived for each type of motion. Predicted infrared and Raman intensities are reported.     

Vibrational frequencies and structural determination of triethynylmethylgermane

The normal mode frequencies and corresponding vibrational assignments of triethynylmethylgermane are examined theoretically using the Gaussian98 set of quantum chemistry codes. Each of the vibrational modes was assigned to one of nine types of motion predicted by a group theoretical analysis Ge-C stretch, C[triple bond]C stretch, C-H stretch, C[triple bond]C-H bend, Ge-C[triple bond]C bend, C-Ge-C bend, H-C-H bend, CH3 wag, and CH3 twist) utilizing the C3v symmetry of the molecule. Uniform scaling factors were derived for each type of motion. Predicted infrared and Raman intensities are reported.     

Elegant approach to spacer arranged silagermylene and bis(germylene) compounds

Herein we report on the reactions of the stable LSiCl (1) and LGeCl (2) [L = PhC(NtBu)(2)] with L(1)Ge, [L(1) = CH{(C[double bond, length as m-dash]CH(2))(CMe)(2,6-iPr(2)C(6)H(3)N)(2)}] (3) to yield 1-sila-5-germylene (4) and a 1,5-bis(germylene) (5). The reactions proceed through the 1,4 nucleophilic addition of the M-Cl (M = Si or Ge) to 3 without any modification of the oxidation state although the change of the oxidation state is thermodynamically more favorable. Compounds 4 and 5 were investigated by single crystal X-ray structural analyses, multi-nuclear NMR spectroscopy, and micro-analysis. Treatment of L(1)AlMe·thf (6) with 1 resulted in the formation of the 1-sila-5-aluminium complex (7). The complex contains a Si(II) and an Al(III) atom in the molecule. All reported reactions proceed without changing the oxidation states at the metal centers.     

Protonation behaviour of chiral tetradentate polypyridines derived from alpha-pinene

Detailed protonation experiments of the [5,6]-pinenebipyridine molecule and the unsubstituted [4,5]- and [5,6]-CHIRAGEN[0] ligands in various solvents indicate a variety of structures of the protonated species. UV-visible and NMR measurements (including (15)N chemical shifts) show the transition from trans to cis conformation of [5,6]-pinenebipyridine upon protonation. The [4,5]-CHIRAGEN[0] ligand, in which the protonation sites of the nitrogen atom donors are at opposite sides of the molecule, behave essentially like two independent bipyridine moieties; this behaviour was monitored by UV-visible, CD and NMR spectroscopy (including (15)N data). In the case of the [5,6]-CHIRAGEN[0], a pocket of donor atoms provides a chiral environment for two protons per ligand.     

Theoretical study on structures and stabilities of [H,Ge,C,N

Theoretical investigations are performed for the first time on the simplest hydrogenated germanium cyanide [H,Ge,C,N], whose analogs [H,C(2),N] and [H,Si,C,N] have been detected in space and laboratory, respectively. The detailed potential energy surfaces in both singlet and triplet states are constructed at the CCSD(T)/6-311+G(3df,2p)//B3LYP/6-31G(d)+ZPVE level, including 18 minimum isomers and 26 interconversion transition states. The former three low-lying and kinetically stabilized isomers are HGeCN (1)1 (0.0 kcal/mol), HGeNC (1)2 (5.1 kcal/mol), and cyclic cCHNGe(1)7 (11.1 kcal/mol). In addition, five isomers HCNGe (1)3 (33.8), HNCGe (1)5 (29.8), cNHCGe (1)8 (37.9), HGeCN (3)1 (30.1), and HNCGe (3)5 (26.5) each have considerable barriers, despite their high energies. Future laboratory characterization and astrophysical detection of the eight [H,Ge,C,N] isomers, especially the former three low-lying species (1)1, (1)2, and (1)7, are highly recommended. The accurate spectroscopic data at the QCISD/6-311G(d,p) level are provided. For some species, the CBS-QB3 calculations are also performed. Wherever possible, comparisons with the analogous [H,C(2),N] and [H,Si,C,N] are made on the structural, energetic, and bonding properties.