Modulation of the Structure and Properties of Uranyl Ion Coordination Polymers Derived from 1,3,5-Benzenetriacetate by Incorporation of Ag(I) or Pb(II)

Reaction of uranyl
nitrate with 1,3,5-benzenetriacetic acid (H3BTA) in the
presence of additional species, either organic bases or their conjugate
acids or metal cations, has provided 12 new crystalline complexes,
all but one obtained under solvo-hydrothermal conditions. The complexes
[C­(NH2)3]­[UO2(BTA)]·H2O (1) and [H2NMe2]­[UO2(BTA)] (2) crystallize as one- or two-dimensional
(1D or 2D) assemblies, respectively, both with uranyl tris-chelation
by carboxylate groups and hydrogen-bonded counterions but different
ligand conformations. One of the bound carboxylate units is replaced
by chelating 1,10-phenanthroline (phen) or 3,4,7,8-tetramethyl-1,10-phenanthroline
(Me4phen) in the complexes [(UO2)3(BTA)2­(phen)3]·4H2O (3) and [(UO2)3­(BTA)2­(Me4phen)3]·NMP·3H2O (4) (NMP = N-methyl-2-pyrrolidone),
which are a 2D network with honeycomb topology and a 1D polymer, respectively.
With silver­(I) cations, [UO2Ag­(BTA)] (5),
a three-dimensional (3D) framework in which the ligand assumes various
chelating/bridging coordination modes, and the aromatic ring is involved
in Ag­(I) bonding, is obtained. A series of seven heterometallic complexes
results when lead­(II) cations and N-chelating molecules are both present.
The complexes [UO2Pb­(BTA)­(NO3)­(bipy)]
(6) and [UO2Pb2­(BTA)2­(bipy)2]·3H2O (7), where bipy is 2,2′-bipyridine, crystallize from the one
solution, as 1D and 2D assemblies, respectively. The two 1D coordination
polymers [UO2Pb­(BTA)­(HCOO)­(phen)] (8 and 9), again obtained from the one synthesis, provide
an example of coordination isomerism, with the formate anion bound
either to lead­(II) or to uranyl cations. Another 2D architecture is
found in [(UO2)2Pb2(BTA)2­(HBTA)­(H2O)2(phen)2]·2H2O (10), which provides a possible example of
a Pb–oxo­(uranyl) “cation–cation” interaction.
While [UO2Pb­(BTA)­(HCOO)0.5(NO3)0.5­(Me2phen)] (11), where
Me2phen is 5,6-dimethyl-1,10-phenanthroline, is a 1D assembly
close to those in 6 and 8, [UO2Pb2(BTA)2­(Me4phen)2] (12), obtained together with complex 4, crystallizes as a 2D network as a result of the high degree of
connectivity provided by the chelating/bridging tricarboxylate ligand.
Emission spectra measured in the solid state display vibronic fine
structure attributable to uranyl luminescence (except for complex 5, in which emission is quenched), with variations in maxima
positions associated with modifications of the uranyl ion environment.

硝酸铀酰（uranyl nitrate）与1,3,5-苯三乙酸（1,3,5-benzenetriacetic acid, H3BTA）在有机碱、其共轭酸或金属阳离子等额外组分存在下反应，得到12种新型结晶配合物，其中仅1种未在溶剂热条件下制备。配合物[C(NH₂)₃][UO₂(BTA)]·H₂O（1）与[H₂NMe₂][UO₂(BTA)]（2）分别形成一维（1D）或二维（2D）组装体，二者均通过羧酸基团对铀酰中心进行三齿螯合，且存在氢键结合的抗衡离子，但配体构象存在差异。在配合物[(UO₂)₃(BTA)₂(phen)₃]·4H₂O（3）与[(UO₂)₃(BTA)₂(Me4phen)₃]·NMP·3H₂O（4）（N-甲基-2-吡咯烷酮，N-methyl-2-pyrrolidone, NMP）中，一个配位的羧酸单元被螯合型1,10-邻菲啰啉（1,10-phenanthroline, phen）或3,4,7,8-四甲基-1,10-邻菲啰啉（3,4,7,8-tetramethyl-1,10-phenanthroline, Me4phen）取代；其中配合物3为具有蜂窝状拓扑结构的二维网络，而配合物4则为一维聚合物。与银(I)阳离子反应可得到[UO₂Ag(BTA)]（5），该配合物为三维（3D）骨架，配体呈现多种螯合/桥联配位模式，且芳环参与了银(I)的成键作用。当体系中同时存在铅(II)阳离子与N-螯合配体时，可得到一系列共7种异金属配合物。由同一反应体系结晶得到的配合物[UO₂Pb(BTA)(NO₃)(bipy)]（6）与[UO₂Pb₂(BTA)₂(bipy)₂]·3H₂O（7）（其中2,2′-联吡啶，2,2′-bipyridine, bipy），分别形成一维与二维组装体。同样从同一合成体系中得到的两种一维配位聚合物[UO₂Pb(BTA)(HCOO)(phen)]（8与9），呈现配位异构现象：甲酸根阴离子分别与铅(II)或铀酰阳离子结合。在[(UO₂)₂Pb₂(BTA)₂(HBTA)(H₂O)₂(phen)₂]·2H₂O（10）中可观察到另一种二维结构，该配合物可能存在铅-氧代（铀酰）“阳离子-阳离子”相互作用。配合物[UO₂Pb(BTA)(HCOO)₀.₅(NO₃)₀.₅(Me2phen)]（11）（其中5,6-二甲基-1,10-邻菲啰啉，5,6-dimethyl-1,10-phenanthroline, Me2phen）为一维组装体，其结构与6和8相近；而与配合物4同步得到的[UO₂Pb₂(BTA)₂(Me4phen)₂]（12）则因螯合/桥联型三羧酸配体提供了高连接性，结晶为二维网络。固态下测得的发射光谱显示出可归因于铀酰发光的振动精细结构（配合物5的发射被猝灭，属于例外），其峰位变化与铀酰离子的配位环境改变相关。