Molecular structures of eight hydrogen bond-mediated minoxidil adducts from different aryl acids

Abstract

Cocrystallization experiments between the widely popular active pharmaceutical ingredient (API) minoxidil and an array of aryl acids coformers were carried out, successfully yielding 8 multi-component samples consisting of 3 co-crystals and 5 salts. Most of them are hydrates. The nature of the samples have been featured by XRD, IR and EA, the melting points were also gauged. The structural and supramolecular aspects are investigated in detail. In all adducts the N-oxide shows various nonbonding contacts. The Hmnd dimer was established at both 1 and 4 by a pair of symmetric NH···O H-bonds. In all cases the minoxidil and coformers were connected by the NH···O/OH···O synthon which is proved to be the highest extensive associates (appearing in 8/8 structures), even in the coexistence of other potentially disruptive non-covalent bonding moieties. Interestingly, the piperidine moieties as effective H-bond acceptor never participated in accepting the H-bonds. The pyrimidine amino also only acts as the H-bond donors.The outcomes unveil that the crystal packing is relied on the strong NH⋯O/OH···O H-bonds. Deep insight into the crystal packing uncovered that a different set of extra ON/OO, CH···C, NH···C, CH···O/CH2O, CHCH/CH2CH/CH2CH2, CH2Cl, CH3-π/CH2-π, NH-π, O-π, and π-π contacts contribute to the stabilization and expansion of the total structures. For the synergism of the various nonbonding forces there had the homo/hetero supramolecular synthons. Some classical graph set notations of R22(9) and R42(8) were present in the relative high frequency.