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.

本研究合成并表征了4种基于位阻型NNN型与NN型给体配体的新型双桥联Cd(II)-叠氮配合物。以三齿胺配体2-甲基喹啉基-2-(乙基-2-吡啶基)甲胺（Meepmqa）与双(2-甲基吡啶基)甲胺（MeDPA）为配体，分别得到具有双EE型和双EO型叠氮桥联结构的双核配合物[Cd₂(Meepmqa)₂(μ₁,₃-N₃)₂(N₃)₂]（1）与[Cd₂(MeDPA)₂(μ₁,₁-N₃)₂(N₃)₂]（2）。以N取代三烷基乙二胺类配体N,N,N'-三乙基乙二胺（Et₃en）与N,N,N'-三甲基乙二胺（Me₃en）为配体时，分别得到具有交替双EO/双EE型以及三EO单EE型叠氮配位模式的一维聚合物链{[Cd₂(Et₃en)₂(μ₁,₁-N₃)₂(μ₁,₃-N₃)₂]}ₙ（3）与{[Cd₄(Me₃en)₄(μ₁,₁-N₃)₆(μ₁,₃-N₃)₂]}ₙ（4）。本研究对上述配合物及相关配合物中叠氮配体的红外不对称伸缩振动νas(N₃)进行了分析，以期预测桥联叠氮根的配位键合模式。本文还报道了配体Meepmqa及其配合物1的荧光性能：配合物1的荧光强度相较于游离配体有所提升，这归因于Meepmqa中喹啉基与Cd(II)形成的强Cd-N配位键，以及对应五元螯合环的刚性结构。