Nanoporous, interpenetrated metal-organic diamondoid networks

Reactions of Cd(NO3)(2). 4H(2)O with 4-cyanopyridine in the presence of eth anol or pyrazine guest molecules under hydro(solvo)thermal conditions affor d two new cadmium coordination polymers, [Cd(isonicotinate)(2)(EtOH)][EtOH] , 1, and [Cd(isonicotinate)(2)(H2O)][pyrazine], 2. The Cd centers in both 1 and 2 are seven-coordinate with distorted pentagonal bipyrimidal structure s via coordination to two pyridyl nitrogen atoms, one oxygen atom from a so lvent molecule, one chelating carboxylate, and one semichelating carboxylat e group. The bridging isonicotinate groups link each Cd center to four adja cent Cd centers, resulting in three-dimensional polymeric networks based on doubly interpenetrated diamondoid structures. One molecule of ethanol or p yrazine is also included in 1 or 2, respectively, to fill the void space le ft within the solid after the twofold interpenetration. Thermogravimetric a nalyses (TGA) showed that the included and coordinated ethanol molecules in 1 could be removed stepwise at 100 and 160 degrees C, respectively. After the removal of the guest ethanol molecules, the resulting nanoporous solid exhibits the same X-ray powder diffraction (XRPD) pattern as 1. Guest ethan ol molecules can be reintroduced into the evacuated sample of 1 via exposur e to ethanol vapor at room temperature. Further heating results in the loss of coordinated ethanol molecules and the collapse of the polymeric network structure. On the other hand, XRPD shows that removal of pyrazine in 2 is accompanied by the loss of the coordinated water molecules and, consequentl y, the collapse of the polymeric network structure. These results demonstra te that nanopores can be designed based on interpenetrated coordinated netw orks. Crystal data for 1: orthorhombic space group Pbca, a = 12.691(1) Angs trom, b = 15.545(1) Angstrom, c = 18.342(1) Angstrom, and Z = 8. crystal da ta for 2: orthorhombic space group Pbca, a = 12.081(1) Angstrom, b = 15.323 (2) Angstrom, c = 19.705(3) Angstrom, and Z = 8.