Modified metal dibenzoylmethanates and their clathrates part III - Novel 4-vinylpyridine-extended metal-dibenzoylmethanate host frameworks: Structure, polymorphism, and inclusion properties

In this contribution we show that host materials based on metal dibenzoylme thanates (DBM) can be extended in a versatile way by decreasing the packing efficiency of the simpler metal DBM's reported earlier. Specifically, this can be accomplished by coordinating two 4-vinylpyridines (4-ViPy) to the m etal (Ni or Co) DBM units to give [M(4-ViPy)(2)(DBM)(2)] host complexes. Th ese display a remarkable polymorphism and an ability to form inclusion comp ounds with a large variety of organic species, Five non-clathrate phases re presenting three polymorphic types and twenty-eight inclusion compounds wit h nineteen guests representing five structural types were isolated and stud ied in varying degrees of detail. The inclusion compounds can be prepared b y recrystallization or by interaction of the solid host with guest vapor. I n the latter case, the process realization, kinetics and final product stro ngly depend on the host polymorph chosen as starting material. Kinetic stud ies executed with powder XRD suggest that transient formation of inclusion compounds may occur even during solvent vapor induced transformation of one guest-free polymorph to another. The beta polymorph of the Ni-host reveals the strongest thratogenic ability as well as a high selectivity towards ce rtain homologues and isomers. Its properties give insight into the concept of "flexible zeolite mimics", or "apohosts", as this empty host form is ene rgetically and structurally predisposed towards inclusion processes. In all eleven (three host and eight clathrate) structures studied by single cryst al X-ray diffraction the [M(4-Vi-Py)(2)(DBM)(2)] complex molecule is trans- configured. In most, the host molecules show effective packing in one dimen sion by forming parallel chains. Guest species are located between the chai ns in cages or channels formed by combining voids in the host molecules bel onging to adjacent chains. The corresponding Ni and Co versions of the comp ounds studied were similar.