The crystal and molecular structure of a europium shift reagent complex, the dipyridine adduct of tris-(2,2,6,6-tetramethylheptane-3,5-dionato)-europium(III), Eu(dpm)3(py)2

Abstract

The crystal structure of the dipyridine adduct of tris-(2,2,6,6-tetramethylheptane-3,5-dionato)europium-(III), Eu(dpm)3(py)2, has been determined so that the principal features of its paramagnetically shifted n.m.r, spectrum could be calculated. The crystals form as triclinic parallelepipeds in space group PT with a= 13.611 (5), b= 17.306 (4), c= 10.493 (7)A, e=93"33 (3), fl= 105.20 (5), and y=94-75 (4) °, with two molecules per unit cell. All unique reflections for which 20< 50 ° were observed using graphite monochromatized Mo Ke radiation and a pulse-height analyzer. The structure was refined by large-block diagonal least-squares methods, using 6840 observed reflections, to an R index of 0"039. Most hydrogen atoms were located, and the remainder have been included at their calculated positions. The Eu(dpm)3(py)2 molecule contains a near twofold axis, and the coordination sphere is best described as a square antiprism. Eu(III) lies 0-3 to 0"4 A out of the molecular planes of four ofthefive ligands. Because of the low symmetry of the complex, two geometric factors are needed to account for the observed n.m.r.shirts.

Seven-coordinate distorted C3v-capped trigonal-prismatic europium(II). Crystal structure of hydrated europium(II)-exchanged sodium zeolite A, Eu5Na2-A

“…are smaller, nearly identical at 69°, somewhat less than the average value found in eight-coordinate square-antiprisma tic complexes. 26 This suggests that the zeolite framework, which requires that three coordination angles of an ion associated with a 6-ring not be too much less than 120°, has kept the coordination number of these ions from being eight, or more. Hydrated Eu5Na2-A has a remarkable structure.…”

Uma metodologia para o projeto teórico de conversores moleculares de luz

“…Para isso, modificamos o potencial repulsivo do "Sparkle" adicionando ao mesmo duas gaussianas, cada uma com três novos parâmetros ajustáveis (GUESA1 , GUESA2 e GUESA3 na subrotina block.f do MOPAC 6.00). A otimização simultânea dos oito parâmetros foi feita também utilizando o método simplex 18,19 cuja função resposta a ser minimizada foi definida como o somatório dos quadrados das diferenças entre os valores calculados e os cristalográficos das distâncias interatômicas do poliedro de coordenação do complexo [Eu(dpm) 3 (py) 2 ], um complexo de n.c.-oito 22 (Fig. 5).…”

Systematics and the Properties of the Lanthanides

“…Approximately one-third of the lanthanide complexes with a CN of 8 involve a S-diketone either as a tetrakis(S-diketone)lanthanide anion [107][108][109][110][111][112][113][114][115] or as a bis adduct of a neutral tris(S-diketone)lanthanide complex [116][117][118][119][120][121][122][123][124][125][126][127][128][129][130].…”

“…With only one exception [123), the base molecules are equivalent and are either water [116][117][118][119][120][121], other oxygen donors [124,128), or aromatic nitrogen bases [125][126][127]129,130].…”