New Zn(II) Coordination Polymers Constructed from Amino-Alcohols and Aromatic Dicarboxylic Acids: Synthesis, Structure, Photocatalytic Properties, and Solid-State Conversion to ZnO

Four new coordination polymers have
been obtained solvothermally
from the reactions of Zn­(NO3)2·6H2O with 1,2-, 1,3-, or 1,4-benzedicarboxylic acids in the presence
of various amino-alcohols: 1∞[Zn2(Htea)2(1,2-bdc)]
(1), 1∞[Zn­(H3tris)­(1,3-bdc)­(CH3OH)]
(2), 3∞[Zn5(Htea)2(1,3-bdc)3(H2O)]·2.6H2O (3), and 3∞[Zn3(H2dea)2(1,4-bdc)3] (4) (H3tea = triethanolamine, H3tris
= tris­(hydroxymethyl)­aminomethane, H2dea = diethanolamine,
1,2-H2bdc =1,2-benzenedicarboxylic acid, 1,3-H2bdc =1,3-benzenedicarboxylic acid, and 1,4-H2bdc =1,4-benzenedicarboxylic
acid). Their crystal structures, thermogravimetric analyses, solid-state
transformation to ZnO and characterization of the resultant zinc oxide
particles are reported. Compounds 1 and 2 show three-dimensional (3D) supramolecular architectures, generated
from the interconnection of the zigzag (in 1) and respectively
the linear (in 2) chains through hydrogen bonding interactions.
The crystal structure of 3 revealed the presence of five
different types of zinc atoms that are successively linked through
carboxilato or alkoxo bridges in a helicoidal chain running along
the crystallographic a axis. Both right-handed (P) and left-handed (M) helices are present
in the crystal, and they are alternately interconnected by pairs of
isophthalato bridges, resulting in channels of hexagonal shape, filled
with water molecules. Compound 4 has a 3D structure in
which linear centrosymmetric {Zn3(H2dea)2}6+ nodes are joined by terephthalate bridges.
Owing to its porous network, compound 3 was tested in
two selective reactions: photooxidation of phenol to hydroquinone
and aerobic photooxidative condensation of benzylamine to N-benzylidenebenzylamine.