Mono- and bimetallic lanthanide(III) phenolic cryptates obtained by template reaction: solid state structure, photophysical properties and relaxivity†
Abstract
We report here a structural and photophysical study of lanthanide monometallic complexes with the macrobicyclic axial phenolic cryptand N[(CH2)2NCH–R–CHN(CH2)2]3N (R = m-C6H2OH-2-Me-5) L as well as of bimetallic complexes with its de-protonated form (L − 3H)3−. The X-ray crystal structure of [DyL(NO3)](NO3)2·2CH3CN· 0.5H2O shows the metal ion being asymmetrically positioned into the macrobicyclic cavity and bonded to seven donor atoms of L and two oxygen atoms of a bidentate nitrate ion. The X-ray crystal structure of the bimetallic cryptate, [Dy2(L − 3H)(NO3)2](NO3)·3H2O·MeOH, confirms that both Dy(III) ions are held into the cavity of the cryptand at a very short distance from each other, 3.4840(4) Å. High resolution laser-excited