Crystal Engineering Studies with Monocarboxamidoalkanes Having C- or N-Terminal Pyridine and Their Coordination Complexes

Crystal structures of series of monopyridyl amides (1–4) are analyzed and compared with those of N,N′-bis(pyridyl)alkanediamides (amides) and N,N′-bis(pyridylcarboxamido)alkane (reverse amides). The amide analogues (1 and 2) are found to form amide-to-amide N–H···O hydrogen bonds, whereas the reverse amide analogues (3 and 4) exhibit N–H···N hydrogen bonds. Furthermore, complexation reactions of 1–4 have been carried out with various metal salts, and the hydrogen-bonding patterns in these crystal structures have been analyzed to compare with those observed in 1–4. The analyses and rationalization of these structures and related derivatives in the Cambridge Structural Database suggested that amide-to-amide recognition is mostly observed with halide metal salts.