Vibrational frequencies and structural determinations of maleonitrile

The vibrational frequencies and corresponding normal mode assignments of maleonitrile are examined theoretically using the GAUSSIAN98 set of quantum chemistry codes. All normal modes were successfully assigned to one of eight types of motion predicted by a group theoretical analysis (C triple bond N stretch, C=C stretch, C-C stretch, C-H stretch, C-H bend, C-C triple bond N bend, C-C triple bond N bend, C-C=C-C torsion) utilizing the C(2v) symmetry of the molecule. The molecular orbitals of maleonitrile are also examined.     

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.     

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 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.     

Vibrational frequencies and structural determination of triethynylmethylsilane

The normal mode frequencies and corresponding vibrational assignments of Triethynylmethylsilane (CH3Si(CCH)3) 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 (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.     

Effects of fluorine on the structures and energetics of the propynyl and propargyl radicals and their anions

[reaction: see text] The adiabatic electron affinity (EA(ad)) of the CH(3)-C[triple bond]C(*) radical [experiment = 2.718 +/- 0.008 eV] and the gas-phase basicity of the CH(3)-C[triple bond]C:(-) anion [experiment = 373.4 +/- 2 kcal/mol] have been compared with those of their fluorine derivatives. The latter are studied using theoretical methods. It is found that there are large effects on the electron affinities and gas-phase basicities as the H atoms of the alpha-CH(3) group in the propynyl system are substituted by F atoms. The predicted electron affinities are 3.31 eV (FCH(2)-C[triple bond]C(*)), 3.86 eV (F(2)CH-C[triple bond]C(*)), and 4.24 eV (F(3)C-C[triple bond]C(*)), and the predicted gas-phase basicities of the fluorocarbanion derivatives are 366.4 kcal/mol (FCH(2)-C[triple bond]C:(-)), 356.6 kcal/mol (F(2)CH-C[triple bond]C:(-)), and 349.8 kcal/mol (F(3)C-C[triple bond]C:(-)). It is concluded that the electron affinities of fluoropropynyl radicals increase and the gas-phase basicities decrease as F atoms sequentially replace H atoms of the alpha-CH(3) in the propynyl system. The propargyl radicals, lower in energy than the isomeric propynyl radicals, are also examined and their electron affinities are predicted to be 0.98 eV ((*)CH(2)-C[triple bond]CH), 1.18 eV ((*)CFH-C[triple bond]CH), 1.32 eV ((*)CF(2)-C[triple bond] CH), 1.71 eV ((*)CH(2)-C[triple bond]CF), 2.05 eV ((*)CFH-C[triple bond]CF), and 2.23 eV ((*)CF(2)-C[triple bond]CF).     

The microwave spectrum of the 1,1-difluoroprop-2-ynyl radical, F2*C-C[triple bond]CH

The rotational spectrum of the 1,1-difluoroprop-2-ynyl radical, F2*C-C[triple bond]CH, a partially fluorinated variant of the propargyl radical, has been recorded in the ground electronic, 2B1, state using pulsed discharge, pulsed-jet, Fabry-Perot Fourier transform microwave spectroscopy. Five successive a-type rotational transitions, from N = 1-0 to N = 5-4, and Ka = 0, 1, and 2, were measured between 6.5 and 32.5 GHz with an uncertainty of 5 kHz. The molecular constants, including fine and hyperfine constants, were precisely determined. These constants are compared with our predictions based on a density functional theory level ab initio calculations and with the fine and hyperfine constants of the propargyl radical. The measured electron spin densities suggest that both the difluoropropargyl and the difluoroallenyl resonance forms [F2*C-C[triple bond]CH<-->F2C=C=C*H] make major contributions to the electronic structure of the radical.     

A combined ab initio and photoionization mass spectrometric study of polyynes in fuel-rich flames

Polyynic structures in fuel-rich low-pressure flames are observed using VUV photoionization molecular-beam mass spectrometry. High-level ab initio calculations of ionization energies for C2nH2 (n=1-5) and partially hydrogenated CnH4 (n=7-8) polyynes are compared with photoionization efficiency measurements in flames fuelled by allene, propyne, and cyclopentene. C2nH2 (n=1-5) intermediates are unambiguously identified, while HC[triple bond, length as m-dash]C-C[triple bond, length as m-dash]C-CH=C=CH2, HC[triple bond, length as m-dash]C-C[triple bond, length as m-dash]C-C[triple bond, length as m-dash]C-CH=CH2 (vinyltriacetylene) and HC[triple bond, length as m-dash]C-C[triple bond, length as m-dash]C-CH[double bond, length as m-dash]CH-C[triple bond, length as m-dash]CH are likely to contribute to the C7H4 and C8H4 signals. Mole fraction profiles as a function of distance from the burner are presented. C7H4 and C8H4 isomers are likely to be formed by reactions of C2H and C4H radicals but other plausible formation pathways are also discussed. Heats of formation and ionization energies of several combustion intermediates have been determined for the first time.     

Carbon-rich molecules: synthesis and isolation of aryl/heteroaryl terminal bis(butadiynes) (HC[triple bond]C-C[triple bond]C-Ar-C[triple bond]C-C[triple bond]CH) and their applications in the synthesis of oligo(arylenebutadiynylene) molecular wires

The synthesis, isolation and characterisation are reported for a series of terminal aryl/heteroaryl bis(butadiynes) (HC[triple bond]C-C[triple bond]C-Ar-C[triple bond]C-C[triple bond]CH) 4a-e including the X-ray molecular structure of the 2,5-pyridylene derivative 4d; compound 4a and the mono-protected analogue [HC[triple bond]C-C[triple bond]C-Ar-C[triple bond]C-C[triple bond]C-C(OH)Me2] 5a serve as convenient precursors for the synthesis of highly-conjugated oligo(arylenebutadiynylene)s.     

Vibrational frequencies and structural determination of tetrafluoroformaldazine

The normal mode frequencies and corresponding vibrational assignments of tetrafluoroformaldazine (F(2)CNNCF(2)) 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 (C-F stretch, C[triple bond]N stretch, N-N stretch, C=C-N bend, CF(2) wag, CF(2) rock CF(2) scissors, CF(2) twist, and C=N-N=C torsion) utilizing the C(2h) symmetry of the molecule. Uniform scaling factors was derived for each type of motion. Predicted infrared and Raman intensities are reported.     

Direct detection of polyynes formation from the reaction of ethynyl radical (C2H) with propyne (CH3-C[triple bond]CH) and allene (CH2=C=CH2)

The reactions of the ethynyl radical (C(2)H) with propyne and allene are studied at room temperature using an apparatus that combines the tunability of the vacuum ultraviolet radiation of the Advanced Light Source at Lawrence Berkeley National Laboratory with time-resolved mass spectrometry. The C(2)H radical is prepared by 193-nm photolysis of CF(3)CCH and the mass spectrum of the reacting mixture is monitored in time using synchrotron-photoionization with a dual-sector mass spectrometer. Analysis using photoionization efficiency curves allows the isomer-specific detection of individual polyynes of chemical formula C(5)H(4) produced by both reactions. The product branching ratios are estimated for each isomer. The reaction of propyne with ethynyl gives 50-70% diacetylene (H-C[triple bond]C-C[triple bond]C-H) and 50-30% C(5)H(4), with a C(5)H(4)-isomer distribution of 15-20% ethynylallene (CH(2)=C=CH-C[triple bond]CH) and 85-80% methyldiacetylene (CH(3)-C[triple bond]C-C[triple bond]CH). The reaction of allene with ethynyl gives 35-45% ethynylallene, 20-25% methyldiacetylene and 45-30% 1,4-pentadiyne (HC[triple bond]C-CH(2)-C[triple bond]CH). Diacetylene is most likely not produced by this reaction; an upper limit of 30% on the branching fraction to diacetylene can be derived from the present experiment. The mechanisms of polyynes formation by these reactions as well as the implications for Titan's atmospheric chemistry are discussed.     

Solvation of LiClO4 and NaClO4 in deuterated acetonitrile studied by means of infrared and Raman spectroscopy

Vibrational characteristics of CD3CN solutions of LiClO4 and NaClO4 have been studied by means of infrared and Raman spectroscopy. Blue shifts of 22 and 11 cm(-1) of the v2 C[triple bond]N stretch are observed resulting from interaction of CD3CN with Li+ and Na+, respectively. The number of primary solvation sites of both Li+ and Na+ in acetonitrile is believed to be four from the comparison of the Raman intensities of the C[triple bond]N stretch for free CD3CN and those coordinated to Li+ and Na+. Evidently formation of contact ion pairs of the cation (Li+ or Na+) and anion (ClO4-) is more probable at a higher concentration of the salt. The characteristics of the v2 C[triple bond]N stretch, v4 C-C stretch, and v8 CCN deformation bands vary substantially upon coordination, while other vibrational bands are relatively immune to the donor-acceptor interaction. DFT calculations have also been performed at the BLYP/6-31 + G(2d,p) level to examine the structures and vibrational characteristics of CD3CN coordinated to Li+ and Na+. The calculated results are in good agreement with the observed vibrational characteristics.     

Vibrational frequencies and structural determination of phosphorous tricyanide

The normal mode frequencies and corresponding vibrational assignments of phosphorous tricyanide (P(CN)(3)) are examined theoretically using the Gaussian98 set of quantum chemistry codes. Each of the vibrational modes was assigned to one of four types of motion predicted by a group theoretical analysis P-C stretch, CN stretch, P-C[triple bond]C bend, and C-P-C bend) utilizing the C(3v) symmetry of the molecule. A uniform scaling factor was derived for each type of motion. Predicted infrared and Raman intensities are reported.     

Bonding rearrangements of hydrogen-bonded complexes involving alkynes

Molecules containing a C-C triple bond, such as HC[triple bond]CH, FC[triple bond]CF, and the C[triple bond]CH radical, are allowed to interact with a partner molecule of H2O, NH3, or HF. Quantum chemical calculations show that these C[triple bond]CH...X H-bonded complexes are bound by up to 4 kcal x mol(-1). More importantly, they can rearrange in such a way that the partner molecule adds to the triple bond so as to form a double C=C bond. Whereas this process is strongly exoergic, there is a high-energy barrier to this rearrangement process. On the other hand, when a second water molecule is added to the complex, it can shuttle protons from the donor part of the complex to the acceptor, and thereby greatly reduce the rearrangement energy barrier. In the case of CCH + 2H2O, this barrier is computed to be less than 4 kcal x mol(-1).     

Insertion of benzyl isocyanide into a Zr-P bond and rearrangement. Atom-economical synthesis of a phosphaalkene

Reaction of (N(3)N)ZrPHPh (N(3)N=N(CH(2)CH(2)NSiMe(3))(3)(3-)) with PhCH(2)N[triple bond]C affords the 1,1-insertion product (N(3)N)Zr[C(PHPh)=NCH(2)Ph], which thermally rearranges to the phosphaalkene-containing complex, (N(3)N)Zr[N(CH(2)Ph)C(H)=PPh].     

Tracking the chemistry of unsaturated C3H3 groups adsorbed on a silver surface: propargyl-allenyl-acetylide triple bond migration, self-hydrogenation, and carbon-carbon bond formation

A diverse array of unsaturated C1 (methylene and methylidyne) and C2 (vinyl, vinylidene, ethylidene, and ethylidyne) bound to metal center(s) and surfaces has received much attention. In sharp contrast to the effort devoted to C1 and C2 ligands, complexes or surfaces bearing C3 fragments have been less explored, especially the M-C3H3 systems, which include propargyl (M-CH2C[triple bond]CH), allenyl (M-CH=C=CH2), and acetylide (M-C[triple bond]CCH3) forms. To understand the bonding and reactivity of these C3 species appended to an extended metal structure, proprargyl bromide (Br-CH2C[triple bond]CH) was utilized as a precursor to generate C3H3 fragments on a Ag(111) surface under ultrahigh vacuum conditions. The molecular transformation process was explored by a combination of temperature-programmed desorption (TPD), reflection absorption infrared spectroscopy (RAIRS), and X-ray photoemission spectroscopy (XPS) techniques. In addition, density functional theory (DFT) calculations were conducted to obtain the optimized geometries and energies for the various surface intermediates. The computed IR spectra facilitated the vibrational mode assignments. TPD spectra show that C3H3(ad) self-hydrogenates to C3H4 around 300 and 475 K, respectively. In addition to hydrogenation, a C-C coupling product C6H6 (2,4-hexadiyne) is also unveiled as part of the desorption feature at 475 K. Identification of the possible C3H4 isomers (propyne and/or allene) was equivocal, but it was circumvented by using an alpha,alpha-dimethyl-substituted propargylic species--(CH3)2(alpha)C-C[triple bond]CH, which results in hydrogenation products, alkynic (CH3)2CH-C[triple bond]CH and allenic (CH3)2C=C=CH2, distinguishable by the mass spectrometry. The substitution experiments clarify that in the normal case the convoluted TPD feature around 300 K, in fact, consists of both allene at 260 K and propyne at 310 K, while the last hydrogenation product at 475 K is solely propyne. The RAIR spectroscopy demonstrates that at 200 K C3H3(ad) on Ag(111) readily adopts the allenyl formalism involving concerted CBr bond scission and [1,3]-sigmatropic migration (i.e., Br-*CH2C[triple bond]CH --> *CH2=C=CH-Ag), in which the sigma bond moves to a new metal location across the pi-periphery. Single hydrogen incorporation to the alpha-carbon of the surface allenyl rationalizes the allene formation at 260 K. When the surface is heated to the range of 250-300 K, both RAIR and XP spectra reveal drastic changes, indicative of a new species whose spectral characteristics could be duplicated by separate measurements from 1-propyn-1-yl iodide (CH3-C[triple bond]C-I) being a direct source for the surface methylacetylide (CH3-C[triple bond]C-Ag). It is thus suggested that allenyl is further reorganized to render acetylide presumably via [1,3]-hydrogen shift (i.e., *CH2=C=CH-Ag --> *CH3=C[triple bond]C-Ag). The presence of this third Ag-C3H3 isomeric form demonstrates an unprecedented propargyl-allenyl-acetylide multiple rearrangements on a metal surface. Migration of the triple bond from the remote terminal position into the chain, through the stage of allenic structure, is driven by thermodynamic stabilities, supported by the DFT total energy calculations. Consequently, the evolutions of propyne at 310 and 475 K, as well as 2,4-hexadiyne (bismethylacetylide), can all be reasoned out.     

C-C coupling reactions in the coordination sphere of rhodium(I) and rhodium(III): New routes for the di- and trimerization of terminal alkynes

The alkynyl(vinylidene)rhodium(I) complexes trans-[Rh(C[triple bond, length as m-dash]CR)(=C=CHR)(PiPr3)2] 2, 5, 6 react with CO by migratory insertion to give stereoselectively the butenynyl compounds trans-[Rh{eta1-(Z)-C(=CHR)C[triple bond, length as m-dash]CR}(CO)(PiPr3)2](Z)-7-9, of which (Z)-7 (R=Ph) and (Z)-8 (R=tBu) rearrange upon heating or UV irradiation to the (E) isomers. Similarly, trans-[Rh{eta1-C(=CH2)C[triple bond, length as m-dash]CPh}(CO)(PiPr3)2] 12 and trans-[Rh{eta1-(Z)-C(=CHCO2Me)C[triple bond, length as m-dash]CR}(CO)(PiPr3)2](Z)-15, (Z)-16 have been prepared. At room temperature, the corresponding "non-substituted" derivative trans-[Rh{eta1-C(=CH2)C[triple bond, length as m-dash]CH}(CO)(PiPr3)2] 18 is in equilibrium with the butatrienyl isomer trans-[Rh(eta1-CH=]C=C=CH2)(CO)(PiPr3)2] 19 that rearranges photochemically to the alkynyl complex trans-[Rh(C[triple bond, length as m-dash]CCH=CH2)(CO)(PiPr3)2] 20. Reactions of (Z)-7, (E)-7, (Z)-8 and (E)-8 with carboxylic acids R'CO2H (R'=CH3, CF3) yield either the butenyne (Z)- and/or (E)-RC[triple bond, length as m-dash]CCH=CHR or a mixture of the butenyne and the isomeric butatriene, the ratio of which depends on both R and R'. Treatment of 2 (R=Ph) with HCl at -40 degrees C affords five-coordinate [RhCl(C[triple bond, length as m-dash]CPh){(Z)-CH=CHPh}(PiPr3)2] 23, which at room temperature reacts by C-C coupling to give trans-[RhCl{eta2-(Z)-PhC[triple bond, length as m-dash]CCH=CHPh}(PiPr3)2](Z)-21. The related compound trans-[RhCl(eta2-HC[triple bond, length as m-dash]CCH=CH2)(PiPr3)2] 27, prepared from trans-[Rh(C[triple bond, length as m-dash]CH)(=C=CH2)(PiPr3)2] 17 and HCl, rearranges to the vinylvinylidene isomer trans-[RhCl(=C=CHCH=CH2)(PiPr3)2] 28. While stepwise reaction of 2with CF3CO2H yields, via alkynyl(vinyl)rhodium(III) intermediates (Z)-29 and (E)-29, the alkyne complexes trans-[Rh(kappa1-O2CCF3)(eta2-PhC[triple bond, length as m-dash]CCH=CHPh)(PiPr3)2](Z)-30 and (E)-30, from 2 and CH3CO2H the acetato derivative [Rh(kappa2-O2CCH3)(PiPr3)2] 33 and (Z)-PhC[triple bond, length as m-dash]CCH=]CHPh are obtained. From 6 (R=CO2Me) and HCl or HC[triple bond, length as m-dash]CCO2Me the chelate complexes [RhX(C[triple bond, length as m-dash]CCO2Me){kappa2(C,O)-CH=CHC(OMe)=O}(PiPr3)2] 34 (X=Cl) and 35 (X=C[triple bond, length as m-dash]CCO2Me) have been prepared. In contrast to the reactions of [Rh(kappa2-O2CCH3)(C[triple bond, length as m-dash]CE)(CH=CHE)(PiPr3)2] 37(E=CO2Me) with chloride sources which give, via intramolecular C-C coupling, four-coordinate trans-[RhCl{eta2-(E)-EC[triple bond, length as m-dash]CCH=CHE}(PiPr3)2](E)-36, treatment of 37with HC[triple bond, length as m-dash]CE affords, via insertion of the alkyne into the rhodium-vinyl bond, six-coordinate [Rh(kappa2-O2CCH3)(C[triple bond, length as m-dash]CE){eta1-(E,E)-C(=CHE)CH=CHE}(PiPr3)2] 38. The latter reacts with MgCl2 to yield trans-[RhCl{eta2-(E,E)-EC[triple bond, length as m-dash]CC(=CHE)CH=CHE}(PiPr3)2] 39, which, in the presence of CO, generates the substituted hexadienyne (E,E)-EC[triple bond, length as m-dash]CC(=CHE)CH=CHE 40.     

Borane reaction chemistry. Alkyne insertion reactions into boron-containing clusters. Products from the thermolysis of [6,9-(2-HC[triple bond]C-C5H4N)2-arachno-B10H12

The stirring of [ortho-(HC[triple bond]C)-C(5)H(4)N] with [nido-B(10)H(14)] in benzene affords [6,9-{ortho-(HC[triple bond]C)-C(5)H(4)N}(2)-arachno-B(10)H(12)] 1 in 93% yield. In the solid state, 1 has an extended complex three-dimensional structure involving intramolecular dihydrogen bonding, which accounts for its low solubility. Thermolysis of 1 gives the known [1-(ortho-C(5)H(4)N)-1,2-closo-C(2)B(10)H(11)] 2 (13%), together with new [micro-5(N),6(C)-(NC(5)H(4)-ortho-CH(2))-nido-6-CB(9)H(10)] 3 (0.4%), [micro-7(C),8(N)-(NC(5)H(4)-ortho-CH(2))-nido-7-CB(10)H(11)] (0.4%) , 4 binuclear [endo-6'-(closo-1,2-C(2)B(10)H(10))-micro-(1(C),exo-6'(N))-(ortho-C(5)H(4)N)-micro-(exo-8'(C),exo-9'(N))-(ortho-(CH(2)CH(2))-C(5)H(4)N)-arachno-B(10)H(10)] (0.5%) 5, and [exo-6(C)-endo-6(N)-(ortho-(CH[double bond]CH)-C(5)H(4)N)-exo-9(N)-(ortho-(HC[triple bond]C)-C(5)H(4)N)-arachno-B(10)H(11)] 6. An improved solvent-free route to 2 is also presented. This set of compounds features an increasing cluster incorporation of the ethynyl moiety, initially by an effective internal hydroboration, affording an arachno to nido and then a nido to arachno:closo sequence of cluster geometry. An alternative low-temperature route to internal hydroboration is demonstrated in the room temperature reaction of [closo-B(11)H(11)][N(n)Bu(4)](2) with CF(3)COOH and [ortho-(HC[triple bond]C)-C(5)H(4)N], which gives [micro-1(C),2(B)-[ortho-C(5)H(4)N-CH(2)]-closo-1-CB(11)H(10)] 7 (40%) in which one carbon atom is incorporated into the cluster; a similar reaction with [ortho-(N[triple bond]C)-C(5)H(4)N] affords [N(n)Bu(4)][7-(ortho-N[triple bond]C-C(5)H(4)N)-nido-B(11)H(12)], 8 (68%) and stirring [ortho-(N[triple bond]C)-C(5)H(4)N] with [nido-B(10)H(14)] quantitatively affords the cyano analogue of 1, [6,9-{ortho-(N[triple bond]C)-C(5)H(4)N}(2)-arachno-B(10)H(12)] 9. All compounds were characterised by single-crystal X-ray diffraction analysis and NMR spectroscopy.     

Solvation of GaCl3 in deuterated acetonitrile studied by means of vibrational spectroscopy

Remarkably large blue shifts of the nu2 C [triple bond] N stretch, nu4 C-C stretch, and nu8 CCN deformation bands of CD3CN are observed in the infrared and Raman spectra of CD3CN solution of GaCl3, resulting from the donor-acceptor interaction of CD3CN with the Lewis acid. The Raman spectrum in the nu2 region shows further details; three new bands emerge on the blue side of the nu2 band of free CD3CN and the relative intensities between the bands vary with concentration, suggesting that there exist at least three different complexes in the solution. Parallel to the nu2 region, similar new bands are observed on the blue sides of the nu4 and nu8 bands of free CD3CN. The strong hydrogen bonds formed between the CD3 group and the chlorine atoms of the solute result in a large band appearing on the low frequency side of the nu1 CD3 symmetric stretch band of free CD3CN. The solvation number of GaCl3, as determined from the Raman intensities of the C [triple bond] N stretch bands for free and coordinated CD3CN, increases from 1.3 to about 1.7 with decreasing concentration.     

Selective binding of the cyano group in acrylonitrile adsorption on Si(100)-2 x 1

The covalent binding of acrylonitrile (CH(2)=CH-C triple bond N) and the formation of a C=C-C=N structure on Si(100) have been investigated using high-resolution electron energy loss spectroscopy (HREELS), X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and density functional theory (DFT) calculations. For chemisorbed acrylonitrile, the absence of nu(C triple bond N) at 2245 cm(-1) and the appearance of nu(C=N) at 1669 cm(-1) demonstrate that the cyano group directly participates in the interaction with Si(100), which is further supported by XPS and UPS observations. Our experimental results and DFT calculations unambiguously demonstrate a [2 + 2] cycloaddition mechanism for acrylonitrile chemisorption on Si(100) through the binding of C triple bond N to Si dimers. The resulting chemisorbed monolayer with a C=C-C=N skeleton can serve as a precursor for further chemical syntheses of multilayer organic thin films in a vacuum and surface functionalization for in situ device fabrication.