Number Of Isotopologues Research Articles

Semiexperimental equilibrium molecular structure of phthalic anhydride

The semiexperimental equilibrium molecular structure (rese) of the title compound is derived from the experimental rotational constants of the parent molecule and a number of isotopologues using a quantum-chemical force field. The quadratic and cubic force fields are calculated at the B2PLYP double hybrid functional with the correlation-consistent triple-ζ cc-pVTZ basis set. The rovibrational and electronic corrections necessary for transformation of ground-state rotational constants to equilibrium ones are calculated using anharmonic (cubic) force constants and rotational g tensor, respectively. The rese structure is used to benchmark the results of coupled-cluster computations (CCSD(T)).

Semiexperimental equilibrium molecular structures of the maleimide and phthalimide

ABSTRACTSemiexperimental (SE) equilibrium molecular structures of the title compounds are determined using rotational and ab initio data. Cubic force constants for the parent molecules and a number of isotopologues are calculated at the B2PLYP double hybrid functional with the correlation-consistent triple-ζ cc-pVTZ basis set. Rovibrational and electronic corrections necessary for the transformation of observed ground-state rotational constants to equilibrium ones are calculated using cubic force constants and rotational g tensors. The SE structure parameters are compared with those obtained with CCSD(T) method and basis set of quadruple-ζ quality.Abbreviations: MP2: Møller–Plesset perturbation theory; CCSD(T): coupled-cluster theory including single and double excitations augmented by a perturbational estimate of the effects of connected triple excitations; VnZ: cc-pVnZ, Dunning's correlation-consistent basis, where n = T or Q; CVnZ: cc-pCVnZ, Dunning's correlation-consistent basis, where n = T or Q; wCVnZ: cc-pwCVnZ, Dunning's correlation-consistent basis, where n = T or Q; AwCVQZ: aug-cc-pwCVQZ, Dunning's correlation-consistent basis; AE: all-electrons; FC: frozen core; QM: quantum mechanics; MAD: mean absolute deviation; SE: semiexperimental equilibrium structure; BO: best ab initio Born–Oppenheimer composite structure; HOMA: harmonic oscillator model of aromaticity; ICSS: iso-chemical shielding surface (isosurface of magnetic shielding value or isosurface of NICS with inverted sign); ICSSZZ: component of magnetic shielding tensor perpendicular to molecular plane; NICS: nuclear independent chemical shift; AIM: atoms in molecules method; ACID: anisotropy of current induced density