Theoretical enthalpies of formation of NHmCln: Neutral molecules, cations, and anions

Ab initio molecular orbital calculations are reported for all neutrals, anions, and cations of the formula NHm (m = 1-3) and for their chlorinated analogues NHmCln (m + n = 1, 2, or 3). Structures were optimized using gradient techniques at HF/6-31++G(d,p) and at MP2(full)/6-311++G(d,p). Single-point calculations are reported at MP4SDTQ(fc)/6-311++G(2df,p) and at QCISD(T)(full)/6-311++G(2df,p) levels using geometries optimized at MP2. Standard enthalpies of formation have been calculated at MP4SDTQ(fc)/6-311++G(2df,p) and at QCISD(T)(full)/6-311++G(2df,p) and, where possible, are compared to experimental and previous theoretical results. These same two levels of theory give adiabatic ionization energies that are within +/- 0.12 eV of experimental values and proton affinities for neutrals and anions that are within at least 3 kcal mol(-1) of experimental values. Electron affinities, anchored on the experimental value of NH, are reported at MP4 and QCl for NCl, NH2, NHCl, and NCl2.