Employing Zinc Clusters as SBUs To Construct (3,8) and (3,14)-Connected Coordination Networks: Structures, Topologies, and Luminescence

Two new metal–organic frameworks (MOFs), [Zn2(OH)­(cpia)­(bipy)0.5]n (1) and {[Zn7(OH)2(HOMe)2(cpia)4(bib)]·5H2O}n (2) (bib = 1,4-bis­(imidazol-1-yl)­benzene,
H3cpia = 5-(4-carboxyphenoxy)­isophthalic acid, bipy = 4,4′-bipyridine),
have been solvothermally synthesized and structurally characterized.
Both of them are based on zinc clusters as secondary building units
(SBUs). Compound 1 presents an interesting three-dimensional
2-fold interpenetrated (3,8)-connected network constructed from tetranuclear
[Zn4(OH)2]6+ clusters with (43)2(46·618·84) topology, while compound 2 can be described
as a (3,14)-connected framework built from an unprecedented heptanuclear
[Zn7(OH)2(HOMe)2]12+ cluster
with {(420·652·76·813)­(43)4} topology. Detailed structural
comparison of two compounds indicated that coligands play significant
roles in tuning the nuclearity of metal clusters and the connectivity
of specific networks. Furthermore, the thermal stabilities and luminescence
properties of two compounds reveal that they all exhibit high thermal
stability and strong luminescence emission bands in the solid state
at room temperature.