SYNTHESIS, CHARACTERIZATION AND STRUCTURE DETERMINATION OF A NEW FLUOROGALLOPHOSPHATE (MU-5) PREPARED IN THE PRESENCE OF 1,4,8,11-TETRAAZACYCLOTETRADECANE

A new fluorinated gallophosphate has been synthesized in aqueous mediu m using the macrocycle 1,4,8,11-tetraazacyclotetradecane (cyclam) as t he organic species. The material has been characterized using elementa l analysis, X-ray diffraction and solid state NMR spectroscopy. Its st ructure was determined in the space group Pbcn (a = 13.373(2) Angstrom , b = 10.447(1) Angstrom, c = 18.538(2) Angstrom) from synchrotron pow der diffraction data using a combination of direct methods and molecul ar modelling techniques. The structure, with the chemical formula [Ga2 0P16O64F8(OH)(4)] . 4C(10)H(24)N(4) per unit cell, consists of galloph osphate sheets of double 4-ring (D4R) units connected to one another t o form 10-rings. Each D4R contains a fluoride ion, and each of the two Ga atoms in the D4R not connected to a neighboring D4R also has a ter minal F- or OH- ion in its coordination sphere. F-19 solid-state NMR s pectroscopy confirmed the presence of two types of fluoride ions. The sheets are connected to one another in an unusual manner via a Ga-cycl am complex. The cyclam molecule of this complex is further stabilized by hydrogen bonds to two terminal F- or OH- ions. All P atoms are tetr ahedrally coordinated and 4-connected (i.e. form oxygen bridges to fou r Ga atoms), whereas the Ga atoms are 5- and 6-coordinated but only 2- , 3- and 4-connected to P atoms of the framework. This new gallophosph ate exhibits low thermal stability, and becomes completely amorphous u pon calcination at 350 degrees C. (C) 1998 Elsevier Science B.V. All r ights reserved.