Coordination Polymers Containing M2L2 and M4L4 Metallacylces of Bis(pyridylcarboxamido)alkanes with an Odd Number of −(CH2)– Groups as Spacers: Guest Inclusion and Networks Recognition via α Sheet

Abstract

The reactions of bis(pyridylcarboxamido)propane (L1, 4-pyridyl and L2, 3-pyridyl), and bis(pyridylcarboxamido)pentane (L3, 4-pyridyl and L4, 3-pyridyl) with Cu(I/II), Co(II), and Cd(II) salts in the presence of various anions resulted in one-dimensional (1D) and two-dimensional (2D) coordination polymers containing M2L2 and M4L4 metallacycles. Reactions of L1 and L2 with CuI afforded the formation of two different kinds of SBUs as Cu2I2 and Cu4I4, and both complexes form 1D chains, which are assembled further by α-sheet hydrogen bonding. The reactions of M(II) salts in the absence of guest molecules lead to the formation of 1D chains containing M2L2-type metallacycles. These 1D chains are found to be of two types: in one type adjacent metallacycles are in plane with each other and in the second type they are nonparallel to each other. The reaction of Cu(II) with L1 in the presence of guest molecules such as benzonitrile or nitrobenzene leads to the formation of corrugated 2D layers containing M4L4 metallacycles. These 2D layers exhibit 2-fold interpenetration as well as guest inclusion simultaneously and also exhibit preferential guest-exchange dynamics. The self-complementary amide groups of the ligands assembled these coordination networks into higher dimensional architectures via amide-to-amide (α-sheet), amide-to-water, amide-to-anions, and N–H···O or O–H···O hydrogen bonds. The alkyl spacers are found to exhibit various conformations depending on the coordination network geometries, anions, and guest molecules.