One-Dimensional Cadmium Polymers with Alternative di(EO/EE) and di(EO/EO/EO/EE) Bridged Azide Bonding Modes

Four
new doubly bridged Cd­(II)-azido complexes derived from sterically
hindered NNN- and NN-donors were synthesized and structurally characterized.
The tridentate amine ligands 2-methylquinolyl-2­(ethyl-2-pyridyl)-methylamine
(Meepmqa) and bis­(2-methylypyridyl)­methylamine (MeDPA) afforded the
dinuclear complexes [Cd2(Meepmqa)2(μ1,3-N3)2(N3)2]
(1) and [Cd2(MeDPA)2(μ1,1-N3)2(N3)2]
(2) with di-EE- and di-EO-azido bridges, respectively.
The N-substituted trialkyl ethylenediamine compounds N,N,N′-triethylethylenediamine
(Et3en) and N,N,N′-trimethylethylenediamine (Me3en) resulted
in the formation of 1D-polymeric chains {[Cd2(Et3en)2(μ1,1-N3)2(μ1,3-N3)2]}n (3) and {[Cd4(Me3en)4(μ1,1-N3)6(μ1,3-N3)2]}n (4) with alternative (di-EO/di-EE)- and di­(EO/EO/EO/EE)-azido
bonding modes. The IR asymmetric stretching vibration, νas(N3) of the azido ligands in these complexes and
in related complexes, were analyzed in an attempt to predict the coordination
bonding mode of the bridged azide. The fluorescence properties of
the ligand Meepmqa and its complex 1 are reported. The
Cd-complex 1 has increased fluorescence intensity compared
to its free ligand. This was attributed to the strong Cd–N
bond of the quinolyl group of Meepmqa and the nonflexibility of the
corresponding five-membered chelate ring.