Synthesis and crystal structures of new lanthanide isonicotinates: coordination polymers and molecular complexes

New coordination polymers [Ce(C5H4NCOO)3(H2O)2] · 0.5C6H4N2 · 1.5H2O, [Ln(C5H4N-COO)3(H2O)2] (Ln = Ce, Pr) and [Ho(C5H4NCOO)2(H2O)4]NO3, and the tetranuclear complex [Ho4(OH)4(C5H4NCOO)6(H2O)8](NO3)2 · 3.5C6H4N2 · 5H2O were prepared by heating aqueous solutions of lanthanide(III) nitrates with 4-cyanopyridine under conditions of hydro-thermal synthesis. X-ray diffraction study demonstrated that the lanthanide atoms in the coordination polymers are bridged in chains through coordination to the carboxyl group of isonicotinic acid. The metal atoms in the tetranuclear complex are bound in pairs by six bidentate isonicotinate ligands.