Vibrational spectra of phenol are calculated with ab initio Hartree−Fock and MP2 methods as well density functional theory (DFT) using the 6-31G(d,p) basis set. A clear-cut assignment vibrational frequencies is reported on potential energy distribution (PED) at three levels. These results compared previously data experiment. Several reassignments suggested for modes: OH bend, 9b, 17a, 8a, 8b. It demonstrated that MP2/6-31G(d,p) level fails in predicting two modes, labeled 14 4 phenol. The...

Weak metal-arene interactions have been investigated in Zn, Cd, Hg, and Ni complexes of meso-tetraaryl m- p-benziporphyrin (1 2) the new compound, m-benziporphodimethene (3). Compounds 1-3 incorporate phenylene moiety into a macrocyclic structure so as to facilitate interaction between arene coordinated metal ion. X-ray studies performed on Cd(II) Ni(II) show that fragment approaches ion at distance much shorter than sum van der Waals radii. In chloronickel(II) m-benziporphyrin, weak agostic...

Systematic studies of the ability a broad family density functional methods applied to hydrogen-bonded complexes have been carried out on hydrogen fluoride dimer. Specifically, calculations performed using basis sets triple-zeta quality with diffuse functions and multiple polarization functions. Various local nonlocal exchange-correlation functionals in order study structure, energetics, vibrational properties The comparison experimental data, also results coming from ab initio...

A b initio calculations are carried out on the complexes H3N–LiF, H3N–LiCl and their analogs H3N–HF H3N–HCl as well isolated subunits. Double-zeta basis sets, augmented by two sets of polarization functions, used in conjunction with second-order Moller–Plesset perturbation theory (MP2) for evaluation electron correlation effects. The Li bonds found to be substantially stronger than H-bonding counterparts, due large measure greater dipole moments LiX Correlation has a effect geometry...

A b initio calculations are carried out for (NH3)2 with a 6-31G**(1p,2d) basis set containing diffuse polarization functions. Electron correlation is included via second-order Mo/ller–Plesset perturbation theory (MP2). At the SCF level, equilibrium R(NN) distance 3.54 Å and interaction energy −2.35 kcal/mol. Inclusion of enhances attraction substantially, increasing to −4.05 kcal/mol reducing intermolecular separation by 0.20 Å. Comparison previous results at level demonstrates variety...

Studies on the abilities of different density functional methods applied to hydrogen-bonded complexes have been carried out water−carbon monoxide complex. Various local and nonlocal exchange-correlation functionals used in investigation structure, energetics, vibrational properties 1:1 A triple-ζ basis set, added with diffuse functions multiple sets polarization (e.g., 6-311++G(2d,2p)), has throughout study. The comparison experimental data from molecular beam measurements also results...

The primary basis set superposition error (BSSE) results from the artificial lowering of energy each subunit a pair by presence ‘‘ghost orbitals’’ its partner. In addition, these ghost orbitals perturb one-electron properties molecule, causing change in interaction energy, an effect known as secondary BSSE which is not corrected counterpoise procedure. and are calculated for interactions NH3 H2O with Li+, using variety different sets. It found that 2° can be quite large, comparable magnitude...

A b initio calculations at the SCF and correlated levels are carried out to characterize potential energy surface of NH3 dimer. The two basis sets used 4-31G* a larger one containing d-functions on N centers, 6-31G** (1p, 2d). only minimum occurring is cyclic C2h structure in which H-bonding protons displaced 42° from N--N axis. contains very shallow valley along direction leading this geometry single linear H bond although there no corresponding arrangement. Despite symmetrically nonpolar...

Abstract Modifications of the standard 6‐31G** basis set as recommended in accompanying paper are found to markedly lower superposition error (BSSE) title complexes, contrast enlargement a triple‐ζ scheme or by addition diffuse sp shell second d‐functions without prior optimization, all which lead BSSE increase. After appropriate correction for correlation and effects, sets (with exception 6‐311G** with their very large BSSE) predict cyclic geometry NH 3 dimer be more stable than linear...

The complexes formed between cis- and trans-HONO isomers ammonia have been observed characterized in argon matrices. Five perturbed HONO vibrations one NH3 deformation vibration were identified for the H3N···HONO-trans complex, H3N···HONO-cis complex. OH stretching complex is ca. 800 cm-1 red-shifted NOH bending 190 blue-shifted with respect to monomer, indicating formation of a very strong molecular hydrogen bond. Theoretical studies structure spectral characteristics H3N··· HONO-cis...

H2O–HCl is studied using a number of basis sets including 6-31G** and variants which are augmented by diffuse sp shell second set d functions on O Cl. Optimization the geometry complex carried out explicitly electron correlation counterpoise correction superposition error (BSSE) at both SCF correlated levels. Correlation strengthens shortens H bond while BSSE leads to an opposite trend; these two effects different magnitude hence cancel one another only partially. ΔH°(298 K) calculated be...

Abstract Basis set superposition error (BSSE) remains one of the major difficulties besetting current ab initio calculations molecular interactions. Despite widespread notion that lowering BSSE to negligible magnitude requires extremely large basis sets, we show simple modifications sets only moderate size (e.g., 6‐31G**) can accomplish same end at much reduced computational expense. These include reoptimization orbital exponents within framework relevant molecules, plus addition a single...

Topological analysis of the Electron Localization Function (ELF) within framework Quantum Chemical Topology (QCT) has been applied to study nature boron–nitrogen bonds. A series 10 compounds have chosen, with B–N bond length ranging between 1.698 Å (B–N) and 1.258 (BN). According Lewis formula three types bonds recognized. These are: single a basin population 1.91 ÷ 2.09e, double BN 3.78 4.28e, triple 5.72 5.74e. In case partial (BN), where formally two or more resonance hybrids be...

The frequency shift of the proton donor in hydrogen bonded complexes is an important quantity which enables to discuss nature bond. Calculations shifts by quantum chemical methods are usually performed within harmonic approximation and therefore comparison with experimental data biased. We have investigated importance anharmonic corrections case twelve either FH or ClH donor. Hartree–Fock, Mo/ller–Plesset second third order (MP2, MP3), density functional theory (DFT), hybrid Hartree–Fock/DFT...

The complexes formed by trans- and cis-HONO isomers with nitrogen carbon monoxide have been observed characterized in argon matrices. Six perturbed trans-HONO vibrations four were identified for both the N2 CO complexes. perturbation of OH group proves that all are hydrogen bonded; blue shifts as compared to monomer indicate OC···HONO structures which atoms acceptor sites. strength interaction, evidenced vibrational modes nitrous acid, increases from cis- trans-isomer monoxide. Theoretical...