Synthetic, Structural, and Spectroscopic Studies on Solids Containing Tris(dipicolinato) Rare Earth Anions and Transition or Main Group Metal Cations

The synthesis and basic characterisation are reported for 85 new solids of the general formula [ML{sub x}][Ln(dipic){sub 3}]{center_dot}nH{sub 2}O (M = Cr or Co; L = urea, ammonia, and various amines; Ln = La-Lu, plus Y; dipic = pyridine-2,6-dicarboxylate). Syntheses of some seven Cs{sub 3}[Ln(dipic){sub 3}] and [N(C{sub 2}H{sub 5}){sub 4}]{sub 3}[Ln(dipic){sub 3}] species are also given. Low-temperature luminescence measurements on a variety of these compounds and full X-ray crystallographic structure determinations for Cs{sub 3}[Eu(dipic){sub 3}]{center_dot}9H{sub 2}O (orthorhombic, space group C222{sub 1}; a = 10.165(2), b = 18.164(4), c = 18.724(4) {angstrom}; Z = 4; R{sub 1} = 0.041 for 1573 {open_quotes}observed{close_quotes} reflections) and [Co(sar)][Eu(dipic){sub 3}]{center_dot}13H{sub 2}O (monoclinic, space group P2{sub 1}/n; a = 10.611(4), b = 26.500(10), c = 17.583(7) {angstrom}; {beta} = 91.97(3){degrees}; Z = 4; R{sub 1} = 0.037 for 7695 {open_quotes}observed{close_quotes} reflections) are described to illustrate the range and complexity of the physical properties of these new materials. Both Cr(III) and Co(III) act as very efficient quenchers of the normally strong [Eu/Tb(dipic){sub 3}]{sup 3{minus}} luminescence, though in at least one system it appears that Cr(III) may act to transfer excitation energy to Ln excited states from its own higher levels while simultaneously deactivating the Ln ion through its lower (doublet) states.