Computed coupling constants in X(CH3)nH(4-n) moieties where X = 13C and 15N+, and n = 0-4: comparisons with experimental data

Seventy-three unique spin-spin coupling constants have been analyzed for the ten species in the two series X(CH3)nH(4-n), where the central atom X is 13C or 15N+. Thirty-seven experimental values have been obtained from the literature, and several new coupling constants have been measured for the methyl-substituted ammonium ions. Both DFT with the B3LYP functional and ab initio EOM-CCSD calculations have been carried out on these same systems. Coupling constants computed by these two methods are in agreement with experimental values. Some problems related to coupling constants for the cationic ammonium systems have been resolved when these were recomputed at EOM-CCSD for complexes in which NH4+ is hydrogen-bonded to H2O molecules.