No abstract

Bi- and multidentate ligands form part of the tools commonly used for designing coordination and supramolecular complexes with desired stereochemistries. Parameters and concepts usually employed include the normalized bite of bidentate ligands, their cis- or trans-coordinating ability, their rigidity or flexibility, or the duality of some ligands that can act in chelating or dinucleating modes. In this contribution we present a structural database study of over one hundred bi- and tridentate ligands that allows us to parametrize their coordinating properties and discuss the relevance of such parameters for the choice of coordination polyhedron or coordination sites.

A new series of eight-coordinated Nd(iii) complexes derived from 4,4,4-trifluoro-1-(naphthalen-2-yl)butane-1,3-dionate and bi-pyridyl ligands revealed multifunctional molecular materials as photoluminescent single-molecule magnets (SMMs).

International audienceThe reaction between the 2-_TTF-fused-1H-benzimidazol-2-yl_ pyridine alkylated with either the di-( pyrazol-1-yl)-4-pyridyl (L-1) or dimethyl-2,2'-bipyridine (L-2) moiety and 1 equiv. of L-n(hfac)(3).2H(2)O (Ln(III) = Dy-III and Yb-III) leads to three dinuclear complexes of formula [Yb-2(hfac)(6)(L-1)].2(CH2Cl2).C6H14 (1) and [Ln(2)(hfac)(6)(L-2)].CH2Cl2 (Ln(III) = Yb-III (2) and Dy-III (3)). The X-ray structures highlight square antiprism (D-4d symmetry) and spherical tricapped trigonal prism (D-3h) for the eight-and nine-coordinated lanthanide ions, respectively. Irradiation of the lowest-energy HOMO -> LUMO ILCT absorption band induced a F-2(5/ 2) -> F-2(7/ 2) Yb-centered emission for 1 and 2. Both Yb-III ions displayed similar emissions in 2 while two distinct emissions, attributed to the two YbIII ions because of their different coordination environments, were observed in 1. Slow magnetic relaxation is detected by dynamic magnetic measurements for 3 with a measured relaxation time tau(0) = 3.7(1.3) x 10(-7) s and an energy barrier Delta = 39.6(2) cm(-1). Taking into account the environment of both DyIII ions in 3, it was expected that both metallic centers displayed similar dynamic magnetic behavior. The latter was rationalized by ab initio CASSCF/SI-SO calculations