Correlation of methane Raman ν1 band position with fluid density and interactions at the molecular level

The CH₄ Raman ν₁ symmetric stretching band position was measured at various temperatures and pressures over the range 1–600 bars and 0.3–22 °C. The ν₁ symmetric stretching band shifts to lower wavenumbers with increasing pressure and/or decreasing temperature, and shows a systematic correlation with density over this same range. Ab initio calculations (MP2/aug‐cc‐pVTZ) show that the changes in peak shape and position reflect fundamental distortion of the methane structure as the density increases. Copyright © 2007 John Wiley & Sons, Ltd.     

Hydrogen bond and internal rotations barrier: DFT study on heavier group‐14 analogues of formamide

A theoretical study on heavier group‐14 substituting effect on the essential property of formamide, strong hydrogen bond with water and internal rotational barrier was performed within the framework of natural bond orbital (NBO) analysis and based on the density functional theory calculation. For heavier group‐14 analogues of formamide (YHONH₂, Y = Si, Ge and Sn), the n_N–π_Y=O conjugation strength does not always reduce as Y becomes heavier, for example, silaformamide and germaformamide have similar strength of delocalization. Heavier formamides prefer being H‐bond donors to form FYO–H₂O complexes to being H‐bond acceptors to form FYH–H₂O complexes. The NEDA analysis indicates that H‐bond energies of FYO–H₂O complexes increase as moving down group 14 due to concurrently stronger charge transfer (CT) and electrostatic attraction and for the FYH–H₂O complexes H‐bond strengths are similar. The model of CTs from FYO to H₂O differs from that at FYH–H₂O complexes, which are contributed not only by aligning lone‐pair orbital of O but also by another lone‐pair orbital. At two lowest lying excited states (the triplet and S₁ excited states), formamide and its heavier analogues form double H‐bonds with H₂O molecule at the same time. The barrier heights of internal rotation become gradually low from C to Sn, formamide (15.73 kcal/mol) > silaformamide (11.73 kcal/mol) > germaformamide (9.45 kcal/mol) > stannaformamide (7.50 kcal/mol) at the CCSD(T)/aug‐cc‐pVTZ//B3LYP/cc‐pVTZ level. NBO analysis indicates that the barrier does not only come from the n_N→π*_YO conjugation, and for heavier analogues of formamide, the n_N→σ*_YO hyperconjugation effect and steric effect considerably contribute to the overall rotational barrier. Copyright © 2013 John Wiley & Sons, Ltd.     

Substituent effect on electron affinity,gas‐phase basicity,and structure of monosubstituted propargyl radicals and their anions: a theoretical study

The substituent effect of electron‐withdrawing groups on electron affinity and gas‐phase basicity has been investigated for substituted propargyl radicals and their corresponding anions. It is shown that when a hydrogen of the α‐CH₂ group or acetylenic CH in the propargyl system is substituted by an electron‐withdrawing substituent, electron affinity increases, whereas gas‐phase basicity decreases. The calculated electron affinities are 0.95 eV (CH?C? CH₂?), 1.15 eV (CH?C? CHF?), 1.38 eV (CH?C? CHCl?), 1.48 eV (CH?C? CHBr?) for the isomers with terminal CH and 1.66 eV (CF?C? CH₂?), 1.70 eV (CCl?C? CH₂?), 1.86 eV (CBr?C? CH₂?) for the isomers with terminal CX at B3LYP level. The calculated gas‐phase basicities for their anions are 378.4 kcal/mol (CH?C? CH₂:^?), 371.6 kcal/mol (CH?C? CHF:^?), 365.1 kcal/mol (CH?C? CHCl:^?), 363.5 kcal/mol (CH?C? CHBr:^?) for the isomers with terminal CH and 362.6 kcal/mol (CF?C? CH₂:^?), 360.4 kcal/mol (CCl?C? CH₂:^?), 356.3 kcal/mol (CBr?C? CH₂:^?) for the isomers with terminal CX at B3LYP level. It is concluded that the larger the magnitude of electron‐withdrawing, the greater is the electron affinity of radical and the smaller is the gas‐phase basicity of its anion. This tendency of the electron affinities and gas‐phase bacisities is greater in isomers with the terminal CX than isomers with the terminal CH. Copyright © 2009 John Wiley & Sons, Ltd.     

Conformational and structural studies of n‐propylamine from temperature dependent Raman and far infrared spectra of xenon solutions and ab initio calculations

The Raman and infrared spectra (4000 to 50 cm^–1) of the gas, liquid or solution, and solid have been recorded of n‐propylamine, CH₃CH₂CH₂NH₂. Variable temperature (−60 to −100 °C) studies of the Raman (1175 to 625 cm^–1) and far infrared (600 to 10 cm^–1) spectra dissolved in liquid xenon were carried out. From these data, the five possible conformers were identified and their relative stabilities obtained with enthalpy difference relative to trans–trans (Tt) for trans–gauche (Tg) of 79 ± 9 cm^–1 (0.9 ± 0.1 kJ/mol); for Gg of 91 ± 26 cm^–1 (1.08 ± 0.3 kJ/mol); for Gg′ of 135 ± 21 cm^–1 (1.61 ± 0.2 kJ/mol); for Gt of 143 ± 11 cm^–1 (1.71 ± 0.1 kJ/mol). The percentage of the five conformers is estimated to be 18% for the Tt, 24 ± 1% for Tg, 23 ± 3% for Gg, 18 ± 1% for Gg′ and 18 ± 1% for Gt at ambient temperature. The conformational stabilities have been predicted from ab initio calculations utilizing several different basis sets up to aug‐cc‐pVTZ from both second‐order Møller–Plesset (MP2, full) and density functional theory calculations by the Becke, three‐parameter, Lee–Yang–Parr method. Vibrational assignments were provided for the observed bands for all five conformers, which are supported by MP2(full)/6‐31G(d) ab initio calculations to predict harmonic force constants, wavenumbers, infrared intensities, Raman activities and depolarization ratios for both conformers. Estimated r₀ structural parameters were obtained from adjusted MP2(full)/6‐311+G(d,p) calculations. The results are discussed and compared with the corresponding properties of some related molecules. Copyright © 2012 John Wiley & Sons, Ltd.     

Comparative DFT study on the role of conformers in the ruthenium alkylidene‐catalyzed ROMP of norborn‐2‐ene

Comparative quantum chemical calculations on the reaction pathways for the formation of ruthena(IV)cyclobutanes from both 1^st‐ and 2^nd‐generation Grubbs catalysts of the general formula RuX₂(L)(L′)(?CH₂) (L = PCy₃ or 1,3‐dimesityl‐4,5‐dihydroimidazolin‐2‐ylidene, L′ = PCy₃) and norborn‐2‐ene (NBE) were carried out on the B3LYP/LACVP** level in dependence on the ligand X = I, Br, Cl, and F. The mechanism proposed by Straub for the formation of (one) active and (three) inactive NBE–Ru–carbene complexes for non‐cyclic alkenes was applied to the cyclic alkene NBE. In RuX₂(PCy₃)₂(?CH₂), the inactive NBE–Ru–carbene complex is energetically more stable than the active one; however, in RuX₂(IMesH₂)(PCy₃)(?CH₂), the active NBE–Ru–carbene complex is more stable than the inactive one. In due consequence, the possible rate limiting barrier for the conversion of the NBE–Ru–carbene complex into the corresponding metallocyclobutane (MCB) is systematically larger in the case of 1^st‐generation Grubbs catalysts than of 2^nd‐generation Grubbs catalysts due to an additional re‐arrangement for the formation of an active π‐complex from the more stable (inactive) conformer. This correlates with the observed reactivity of both types of initiators. There is a strong influence of the ligands L and X on the conformational properties and relative stabilities of the 14‐electron intermediates, which has a direct effect on the distribution of the inactive and active conformations of the corresponding Ru–carbene–NBE complexes. A direct correlation between the conformational properties of the 14‐electron intermediates and the relative stabilities of the active Ru–carbene–NBE complexes was observed. Copyright © 2008 John Wiley & Sons, Ltd.     

Conformational,vibrational, and structural studies of 2,2,3,3,3‐pentafluoropropylamine from Raman and infrared spectra of gas,liquid, xenon solutions,and solid supported by ab initio calculations

The Raman and infrared spectra (3500–50 cm⁻¹) of the gas, liquid or solution, and solid were recorded of 2,2,3,3,3‐pentafluoropropylamine (CF₃CF₂CH₂NH₂) and the ND₂ isotopomer. Variable temperature (−55 to − 100 °C) studies of the infrared spectra (3600–400 cm⁻¹) of samples dissolved in liquid xenon have been carried out. From these data, two of the five possible conformers have been identified and their relative stabilities obtained. The enthalpy difference was determined between the more stable Tt conformer and the less stable Tg form to be 280 ± 14 cm⁻¹ (3.35 ± 0.17 kJ/mol). The first indicator is the NCCC dihedral angle (G = gauche or T = trans), and the second one (g = gauche or t = trans) is the relative position of the lone pair of electrons on nitrogen with respect to the β‐carbon. The percentage of the Tg conformer at ambient temperature is estimated to be 34 ± 2%. The conformational stabilities have been predicted from ab initio calculations utilizing several different basis sets up to aug‐cc‐pVTZ for both MP2(full) and density functional theory calculations by the B3LYP method. Vibrational assignments have been provided for most of the observed bands for both isotopomers, supported by MP2(full)/6‐31G(d) ab initio calculations to predict the harmonic force fields, wavenumbers, infrared intensities, Raman activities, and depolarization ratios for both conformers. Estimated r₀ structural parameters were obtained from adjusted MP2(full)/6‐311 + G(d,p) calculations. The results are discussed and compared with the corresponding properties of some related molecules. Copyright © 2011 John Wiley & Sons, Ltd.     

A vibrational spectroscopic investigation of rhodanine and its derivatives in the solid state

Raman and infrared spectra are reported for rhodanine, 3‐aminorhodanine and 3‐methylrhodanine in the solid state. Comparisons of the spectra of non‐deuterated/deuterated species facilitate discrimination of the bands associated with N H, NH₂, CH₂ and CH₃ vibrations. DFT calculations of structures and vibrational spectra of isolated gas‐phase molecules, at the B3‐LYP/cc‐pVTZ and B3‐PW91/cc‐pVTZ level, enable normal coordinate analyses in terms of potential energy distributions for each vibrational normal mode. The cis amide I mode of rhodanine is associated with bands at ∼1713 and 1779 cm⁻¹, whereas a Raman and IR band at ∼1457 cm⁻¹ is assigned to the amide II mode. The thioamide II and III modes of rhodanine, 3‐aminorhodanine and 3‐methylrhodanine are observed at 1176 and 1066/1078; 1158 and 1044; 1107 and 984 cm⁻¹ in the Raman and at 1187 and 1083; 1179 and 1074; 1116 and 983 cm⁻¹ in the IR spectra, respectively. Copyright © 2010 John Wiley & Sons, Ltd.     

Theory of electronic structure and nuclear quadrupole interactions in the BF3–NH3 complex and methyl derivatives

Magnetic Hyperfine and Nuclear Quadrupole Interactions (HFI and NQI) are now important tools for characterization of systems of interest in materials research and industry. Boron-Trifluoride is an inorganic compound that is very important in this respect as a catalyst in chemical physics research and industry, forming complexes in the process with compounds like ammonia, water and methyl alcohol. The present paper deals with the BF₃–NH₃ complex and methyl derivatives BF₃NH_x(CH₃)_3?x for which we have studied the electronic structures, binding energies, and ¹⁹F* (I?=?5/2) nuclear quadrupole interactions using the first-principles Hartree–Fock–Roothaan procedure combined with electron correlation effects. Our results for the ¹⁹F* nuclear quadrupole coupling constant (e ² qQ/h) in units of MHz compare well with experiment. Trends in the binding energies and NQI parameters between the complexes are discussed.     

Gas‐phase oxidation of CH2 = C(CH3)CH2Cl initiated by OH radicals and Cl atoms: kinetics and fate of the alcoxy radical formed

Relative kinetics of the reactions of OH radicals and Cl atoms with 3‐chloro‐2‐methyl‐1‐propene has been studied for the first time at 298 K and 1 atm by GC‐FID. Rate coefficients are found to be (in cm³ molecule^?1 s^?1): k₁ (OH + CH₂ = C(CH₃)CH₂Cl) = (3.23 ± 0.35) × 10^?11, k₂ (Cl + CH₂ = C(CH₃)CH₂Cl) = (2.10 ± 0.78) × 10^?10 with uncertainties representing ± 2σ. Product identification under atmospheric conditions was performed by solid phase microextraction/GC‐MS for OH reaction. Chloropropanone was identified as the main degradation product in accordance with the decomposition of the 1,2‐hydroxy alcoxy radical formed. Additionally, reactivity trends and atmospheric implications are discussed. Copyright © 2015 John Wiley & Sons, Ltd.     

Electrochemical properties and radical anions of carbocycle‐fluorinated quinoxalines and their substituted derivatives

Electrochemical reduction (ECR) and oxidation (ECO) of 5,6,7,8‐tetrafluoroquinoxaline ( 1 ) and its derivatives bearing various substituents R (7‐H ( 2 ), 7,8‐H₂ (3 ), 6‐CF₃ ( 4 ), 6‐Cl ( 5 ), 5,7‐Cl₂ ( 6 ), 5‐NH₂ ( 7 ), 6‐OCH₃ ( 8 ), 6,7‐(OCH₃)₂ ( 9 ), 6,7,8‐(OCH₃)₃ ( 10 ), 5,6,7,8‐(OCH₃)₄ ( 11 ), 6‐OCH₃,7‐N(CH₃)₂ ( 12 ), 6‐N(CH₃)₂ ( 13 ), 6,7‐(N(CH₃)₂)₂ ( 14 ), 5,6,7‐(N(CH₃)₂)₃ ( 15 ), and 7,8‐cyclo‐(=CF‐CF = CF‐CF=) ( 16 )) in the carbocycle have been studied by cyclic voltammetry in MeCN. For 1 – 4 and 7 – 15 , the first reduction peaks have been found to be 1‐electron and reversible, thus corresponding to the formation of their radical anions (RAs), which are long lived at 295 K except those of 4 – 6 and 15 , 16 . Irreversible hydrodechlorination has been observed for 5 and 6 at the first step of their ECR confirmed by EPR detection of corresponding RAs of 2 and 5,7‐H₂ derivative of 1 ( 17 ) at the next steps. Electrochemically generated RAs of 1 – 3 , 7 – 14 , and 17 have been characterized in MeCN by EPR spectroscopy together with DFT calculations at the (U)B3LYP/6‐31 + G(d) level of theory using PCM to describe the solvent. A noticeable alternation of spin density on the –NCCN– moiety of quinoxaline has been observed for all RAs possessing R‐substitution asymmetry. The comparative electron‐accepting ability of 1 – 15 has been analyzed in terms of their experimental reduction peak potentials and the (U)B3LYP/6‐31 + G(d)‐calculated gas‐phase first adiabatic electron affinities (EAs). The differences in electron transfer solvation energies for 1 – 15 have been evaluated on the basis of ECR peaks' potentials and calculated gas‐phase EAs. The ECO of 1 – 5 and 7 – 14 has been found to be irreversible.     

Theoretical studies on 2‐(5‐amino‐3‐nitro‐1,2,4‐triazolyl)‐3,5‐dinitropyridine (PRAN) and its derivatives

In this work, a set of derivatives of 2‐(5‐amino‐3‐nitro‐1,2,4‐triazolyl)‐3,5‐dinitropyridine (PRAN) with different energetic substituents (?N₃, –NO₂, –NH₂, –NF₂) have been studied at the Becke, three‐parameter, Lee–Yang–Parr/aug‐cc‐pvdz, Becke, three‐parameter, Lee–Yang–Parr/6‐31G(d), Becke, three‐parameter, Perdew 86/6‐31G(d), and Becke three‐parameter, Perdew–Wang 91/6‐31G(d,p) levels of density functional theory. The gas‐phase heats of formation were predicted with isodesmic reactions and the condensed‐phase HOFs were estimated with the Politzer approach. The effects of different functionals and basis sets were analyzed. –N₃ and –NO₂ greatly increase while –NH₂ and –NF₂ slightly decrease heats of formation. An analysis of the bond dissociation energies and impact sensitivity shows that all compounds have good stability. The crystal densities (1.82–2.00 g/cm³) computed from molecular packing calculations are big for all compounds and that of the –NF₂ derivative is the largest. All derivatives have higher detonation velocity and detonation pressure than PRAN. Compounds 3 and 4 (R = NO₂ and NF₂) have better performance than hexahydro‐1,3,5‐trinitro‐1,3,5‐trizine and the performance of 4 is quite close to that of 1,3,5,7‐tetranitro‐1,3,5,7‐tetraazacyclooctane, they are promising candidates of high energy compounds and worth further investigations. Copyright © 2012 John Wiley & Sons, Ltd.     

Counter anion effect on structural,opto-electronic and charge transport properties of fused π-conjugated imidazolium compound

The structure–activity relationship of fused π-conjugated imidazolium cation with three counter anion molecules, BF₄^?, CF₃SO₃^? and (CF₃SO₂)₂N^?, was studied using electronic structure calculations. The structural, opto-electronic and charge transport properties of these complexes were studied. The charge transfer from π-conjugated imidazolium(I) to counter anion was confirmed in all the studied complexes. Interaction energy varies significantly depending on the counter anion and the stability was found higher for I-BF₄ complex than both I–CF₃SO₃ and I–(CF₃SO₂)₂N complexes. The strong (C–H)⁺···F^? hydrogen bond of length 1.95 Å between fused π-conjugated imidazolium and BF^?₄ anion is the driving force for the strongest interaction energy in I–BF₄ complex. The energy decomposition analysis confirms that the interaction between imidazolium and counter anion is mainly driven by electrostatic and orbital interaction. It has been observed that the absorption spectra of the complex are independent of anion nature but the influence of anion character is observed on frontier molecular orbital pattern. The charge transport property of I–BF₄ complex was studied by using tight-binding Hamiltonian approach and found that the hole mobility in I–BF₄ is 1.13 × 10^?4 cm² V^?1 s^?1.     

Catalysis by hydrogen chloride in the gas‐phase elimination kinetics of 2‐phenyl‐2‐propanol and 3‐methyl‐1‐buten‐3‐ol

A homogeneous, molecular, gas‐phase elimination kinetics of 2‐phenyl‐2‐propanol and 3‐methyl‐1‐ buten‐3‐ol catalyzed by hydrogen chloride in the temperature range 325–386 °C and pressure range 34–149 torr are described. The rate coefficients are given by the following Arrhenius equations: for 2‐phenyl‐2‐propanol log k₁ (s^?1) = (11.01 ± 0.31) ? (109.5 ± 2.8) kJ mol^?1 (2.303 RT)^?1 and for 3‐methyl‐1‐buten‐3‐ol log k₁ (s^?1) = (11.50 ± 0.18) ? (116.5 ± 1.4) kJ mol^?1 (2.303 RT)^?1. Electron delocalization of the CH₂?CH and C₆H₅ appears to be an important effect in the rate enhancement of acid catalyzed tertiary alcohols in the gas phase. A concerted six‐member cyclic transition state type of mechanism appears to be, as described before, a rational interpretation for the dehydration process of these substrates. Copyright © 2007 John Wiley & Sons, Ltd.     

Trissarcosine barium(2 + ) dibromide—a new complex of N‐methylglycine

We obtained a new complex containing sarcosine (CH₃NH₂⁺CH₂COO⁻) and barium(2 + ) dibromide (TSBB) in 3:1 molar ratio, as well as its deuterated analog. Single‐crystal X‐ray diffraction measurements show that TSBB crystallizes in the monoclinic system, space group P2(1)/c. The unit cell parameters are as follows: a = 18.345(4) Å, b = 10.668(2) Å, c = 8.9212(18) Å, β = 91.86(3)°, and Z = 4. The structure was determined with final R₁ = 0.0396 (for I > 2σI). The crystal possesses a pseudohexagonal symmetry down c axis showing the resemblance to the crystal structure of trissarcosine calcium chloride (TSCC). There are N HBr hydrogen bonds (HB) of six types. TSBB crystal undergoes a phase transition at 416 K (heating)–415 K (cooling) of continuous nature. The spectroscopic [Infrared (IR) and Raman] investigation of the crystal was performed at room temperature. The results are discussed with respect to the crystallographic data, as well as the results obtained for TSCC crystal. Copyright © 2008 John Wiley & Sons, Ltd.     

Understanding halogen‐substituent assistance in H‐atom abstraction‐based reactions of CHCl•− with CH4 − nXn (X = H,F, Cl; n = 0–3)

The effect of halogen‐substituent on hydrogen abstraction mechanisms was studied by applying density functional theory functional calculations to the gas‐phase reactions between CHCl^?? and CH_{4 ? n}X_n (X = H, F, Cl; n = 0–3), and it is found that a heavier X substituent in the substrate results in a greater stabilization of corresponding complex, a lower activation energy, a faster H‐abstraction reaction, and greater exothermicity. However, CH₄– reaction is more reactive than CH₃F– reaction under the same condition because of dominant π‐donation from the electronegative F atom. We also explored the reactivity difference for the seven reactions in terms of factors derived from bond order, second‐order perturbative energy, and activation strain model analysis. The rate constants are evaluated over a wide temperature range of 298–1000 K by the conventional transition state theory. Copyright © 2014 John Wiley & Sons, Ltd.     

Stable silicon‐centered localized singlet 1,3‐diradicals XSi(GeY2)2SiX: theoretical predictions

Some localized singlet 1,3‐σ‐diradicals, XSi(GeY₂)₂SiX, (X = H, CH₃, SiH₃, C(CH₃)₃, NH₂ for X = F; Y = H, CH₃, OH, NH₂, SiH₃ for X = H) are theoretically designed by the orbital phase theory, the density functional theory (DFT) calculations , the second order Møller–Plesset perturbation theory (MP2), and the complete active space self‐consistent field (CASSCF) methods. The silicon‐centered singlet diradicals are more stable than the lowest triplets and than the bicylic σ‐bonded isomers if the isomers exist. The most stable singlet diradicals are not the π‐type diradicals, but the σ‐type diradicals where the radicals interact with each other through the Si? Ge bonds in the four‐membered rings. Copyright © 2007 John Wiley & Sons, Ltd.     

Introducing boranorcaradienes with more stability than their corresponding borepins: Reversal of tautomerization via substituents at theoretical levels

In contrast to typical borepins, which appear about 40.0 kcalmol^?1 more stable than their corresponding tautomeric boranorcaradienes, we have found 2 species, which have reversed this trend and pushed the equilibrium in favor of their corresponding boranorcaradienes. They are namely 1a,9b‐dihydro‐1H‐borireno[2,3‐h]pyridazino[4,3‐f]cinnoline and 1a,9b‐dihydro‐1H‐borireno[2,3‐h]pyrimido[5,4‐f]quinazoline which stand up among 14 isomeric systems probed, at B3LYP/AUG‐cc‐pVTZ, M06‐2X/AUG‐cc‐pVTZ, MP2/AUG‐cc‐pVTZ, and HF/AUG‐cc‐pVTZ. Energy barriers are calculated in gas‐phase, where the possibility of a rapid interconversion of the isomers is ruled out. Generally, dibenzoboranorcaradienes assume C_s symmetry with planar geometry and dihedral angle of zero degree. In contrast, their corresponding borepins show a high tendency for puckering with dihedral angle of ~66°. The preference of the latter for puckered non‐planar geometries is evidenced by natural bonding orbitals calculations and visually through their frontier molecular orbitals. Main interactions appear to be hyperconjugations of σ and π bonds across the rings. Position and number of nitrogen atoms on the fused rings seem to affect the energy gap, dipole moment, symmetry, dihedral angle, the chemical shift, NICS, bond lengths, and charge distribution.     

Vibrational spectroscopy and DFT calculations of N,N′‐dicyclohexylcarbodiimide

Infrared (IR) and Raman spectra were obtained for N,N′‐dicyclohexylcarbodiimide (DCC) in the solid state and in CHCl₃ solution. Structures and vibrational spectra of isolated, gas‐phase DCC molecules with C₂ and C_i symmetries, computed at the B3‐LYP/cc‐pVTZ level, show that the IR and Raman spectra provide convincing evidence for a C₂ structure in both the solid state and in CHCl₃ solution. Using a scaled quantum‐chemical force field, these density functional theory calculations have provided detailed assignments of the observed IR and Raman bands in terms of potential energy distributions. Comparison of solid‐state and solution spectra, together with a Raman study of the melting behaviour of DCC, revealed that no solid‐state effects were evident in the spectra. Copyright © 2010 John Wiley & Sons, Ltd.     

Copper(I) Complexes of N-(2-{[(2E)-2-(4-Nitrobenzylidenyl)Hydrazinyl]Carbonyl}Phenyl)Benzamide and Triphenylphosphine: Synthesis,Characterization and Luminescence Properties

Copper(I) complexes of the formula [Cu(L)(PPh₃)₂]X (1–4) (X = Cl(1), ClO₄(2), BF₄(3) and PF₆(4)) [where L = N-(2-{[(2E)-2-(4-nitrobenzylidenyl)hydrazinyl]carbonyl}phenyl)benzamide; PPh₃ = triphenylphosphine] have been prepared by the condensation of N-[2-(hydrazinocarbonyl)phenyl]benzamide with 4-nitrobenzaldehyde followed by the reaction with CuCl, [Cu(MeCN)₄]ClO₄, [Cu(MeCN)₄]BF₄ and [Cu(MeCN)₄]PF₆ in presence of triphenylphosphine as a coligand. Complexes 1–4 were then characterized by elemental analyses, FTIR, UV-visible and ¹H NMR spectroscopy. Mononuclear copper(I) complexes 1–4 were formed with L in its keto form by involvement of azomethine nitrogen and the carbonyl oxygen along with two PPh₃ groups. A single crystal X-ray diffraction study of the representative complex [(Cu(L)(PPh₃)₂]CIO₄ (2) reveals a distorted tetrahedral geometry around Cu(I). Crystal data of (2): space group = C2/c, a = 42.8596 (9) Å, b = 14.6207 (3) Å, c = 36.4643 (7) Å, V = 20,653.7 (7) ų, Z = 16. Complexes 1–4 exhibit quasireversible redox behaviour corresponding to a Cu(I)/Cu(II) couple. All complexes show blue-green emission as a result of fluorescence from an intra-ligand charge transition (ILCT), ligand to ligand charge transfer transition (LLCT) or mixture of both. Significant increase in size of the counter anion shows marked effect on quantum efficiency and lifetime of the complexes in solution.     

Raman and infrared,microwave spectra,conformational stability,adjusted r0 structural parameters,and vibrational assignments of cyclopentylamine

Fourier transform microwave spectrum of cyclopentylamine, c–C₅H₉NH₂ has been recorded, and seven transitions have been assigned for the most abundant conformer, and the rotational constants have been determined: A = 4909.46(5), B = 3599.01(4), and C = 2932.94(4). From the determined microwave rotational constants and ab initio MP2(full)/6‐311 + G(d,p) predicted structural values, adjusted r₀ parameters are reported with distances (Å): rC_α–C_β = 1.529(3), rC_β–C_γ = 1.544(3), rC_γ–C_γ = 1.550(3), rC_α–N = 1.470(3), and angles (°) ∠CCN = 108.7(5), ∠C_βC_αC_β = 101.4(5), and τC_βC_αC_β′C_γ′ = 42.0(5). The infrared spectra (4000–220 cm⁻¹) of the gas have been recorded. Additionally, the variable temperature (−60 to −100 °C) Raman spectra of the sample dissolved in liquefied xenon was recorded from (3800–50 cm⁻¹). The four possible conformers have been identified, and their relative stabilities obtained with enthalpy difference relative to t‐Ax of 211 ± 21 cm⁻¹ for t‐Eq ≥ 227 ± 22 cm⁻¹ for g‐Eq ≥ 255 ± 25 cm⁻¹ for g‐Ax. The percentage of the four conformers is estimated to be 53% for the t‐Ax, 11 ± 1% for t‐Eq, 20 ± 2% for g‐Ax and 16 ± 2% for g‐Eq at ambient temperature. The conformational stabilities have been predicted from ab initio calculations by utilizing several different basis sets up to aug‐cc‐pVTZ from both MP2(full) and density functional theory calculations by the B3LYP method. Vibrational assignments have been provided for the observed bands for all four conformers, which are predicted by MP2(full)/6‐31G(d) ab initio calculations to predict harmonic force constants, wavenumbers, infrared intensities, Raman activities, and depolarization ratios for all of the conformers. The results are discussed and compared to the corresponding properties of some related molecules. Copyright © 2014 John Wiley & Sons, Ltd.