LAUSR

ABSTRACT Semiexperimental (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 GRAPHICAL ABSTRACT