Puckered-Boat Conformation Hexameric Water Clusters Stabilized in a 2D Metal−Organic Framework Structure Built from Cu(II) and 1,2,4,5-Benzenetetracarboxylic Acid

1,2,4,5-Benzenetetracarboxylic acid (btcH4) reacts with Cu(NO3)2·6H2O to form 2D coordination polymeric structure {[Cu2(btc)(Py)4·2H2O]·4H2O}n, 1, in the presence of pyridine from water at room
temperature. Puckered-boat-shaped hexameric water clusters
resulting from four free water molecules and two water molecules
coordinating to metal ions join these sheets to make a 3D network.
These water clusters behave as pillars to join those sheets which
is the key factor stabilizing the 3D network. Thermal analysis, X-ray
powder diffraction, and X-ray structure analysis have been used
to characterize this compound. Crystal data for 1 follow:  triclinic
space group P1̄, a = 8.905(3) Å, b = 11.137(4) Å, c = 17.484(2)
Å, α = 82.342(6)°, β = 81.312(3)°, γ = 82.361(4)° V=
1687.5(1)Å3, Z = 2, R1 = 0.0331, wR2 = 0.0886, S =1.066.