DFT calculations on the hydrogen bonding interactions between adrenaline and trimethoxysilylpropylamine

The hydrogen bonding interactions between adrenaline (Drug) and 3-(trimethoxysilyl)-1-propanamine (TMSA) have been calculated using Gaussian 98 software. Ten possible forms (1–10) for the hydrogen bonding interactions were computed at HF and B3LYP levels of theory with 6-31 G(d) and 6-31 + G(d,p) standard basis sets. The binding energies, ΔE_(binding), were obtained from the equation ΔE_(binding) = E_(complex) − [E_(Drug) + E_(TMSA)] + BSSE. The most stable forms (complexes 4 and 5) interact through O–H … N hydrogen bond, with calculated binding energies at B3LYP/6-31G* level equal to −10.93 and −12.84 kcal mol⁻¹, respectively. Other compounds containing N–H … N (1), N–H … O (2, 3, 6, 9) and O–H … O (7, 8 and 10) hydrogen bonds show lower ΔE_(binding) values. The nuclear quadrupole coupling constants (NQCCs or χs) were calculated for ¹⁷O, ¹⁴N and ²H nuclei about 10.0, 4.0–5.0 MHz and 180.0–360.0 kHz, respectively, that are in agreement with the experimental data.