Uranyl and Uranyl–3d Block Cation Complexes with 1,3-Adamantanedicarboxylate: Crystal Structures, Luminescence, and Magnetic Properties

The
reaction of 1,3-adamantanedicarboxylic acid (LH2) with
uranyl nitrate under solvo-hydrothermal conditions, either alone or
in the presence of additional metal cations (Co2+, Ni2+, or Cu2+) gives a series of nine complexes displaying
a wide range of architectures. While [UO2(L)­(H2O)]·1.25CH3CN (1) and [UO2(L)­(DMF)] (2) are one-dimensional (1D) species analogous
to that previously known, [H2NMe2]2[(UO2)2(L)3]·1.5H2O (3), which includes dimethylammonium counterions generated
in situ, is a three-dimensional (3D) framework, and [UO2(L)­(NMP)] (4) (NMP = N-methyl-2-pyrrolidone)
is a braid-shaped 1D polymer. When 3d block metal ions are present
and bound to 2,2′-bipyridine (bipy) coligands, their role is
reduced to that of decorating species attached to uranyl-containing
1D polymers, as in [UO2M­(L)2(bipy)2]·0.5H2O with M = Co (5) or Ni (6), and [(UO2)2Cu2­(L)3(NO3)2(bipy)2]·0.5H2O (9), or of counterions, as in [Ni­(bipy)3]­[(UO2)4­(O)2(L)3]·3H2O (7), in which a two-dimensional
(2D) assembly is built from tetranuclear uranyl-containing building
units. In contrast, the heterometallic 3D framework [UO2Cu­(L)2] (8) can be isolated in the absence
of bipy. The emission spectra measured in the solid state display
the usual uranyl vibronic fine structure, with various degrees of
resolution and quenching, except for that of complex 7, which shows emission from the nickel­(II) centers. The magnetic
properties of complexes 5, 6, 8, and 9 were investigated, showing, in particular, the
presence of zero-field splitting effects in 6 and weak
antiferromagnetic interactions in 9.

1,3-金刚烷二甲酸（LH₂）与硝酸铀酰在溶剂热条件下单独反应，或添加额外金属阳离子（Co²+、Ni²+或Cu²+）后反应，得到九种结构各异的配合物。配合物1([UO₂(L)(H₂O)]·1.25CH₃CN)与2([UO₂(L)(DMF)])均为一维（1D）物种，结构与此前报道的同类配合物类似；而含原位生成二甲基铵抗衡离子的配合物3([H₂NMe₂]₂[(UO₂)₂(L)₃]·1.5H₂O)为三维（3D）骨架结构；配合物4([UO₂(L)(NMP)]，其中NMP为N-甲基-2-吡咯烷酮)则为辫状一维聚合物。当引入3d过渡金属离子并与2,2′-联吡啶（bipy）辅助配体配位时，这类金属离子的作用仅为作为修饰基团连接于含铀酰的一维聚合物上，如M=Co的配合物5([UO₂M(L)₂(bipy)₂]·0.5H₂O)、M=Ni的配合物6([UO₂M(L)₂(bipy)₂]·0.5H₂O)以及配合物9([(UO₂)₂Cu₂(L)₃(NO₃)₂(bipy)₂]·0.5H₂O)；或是作为抗衡离子，如配合物7([Ni(bipy)₃][(UO₂)₄(O)₂(L)₃]·3H₂O)，该配合物由四核含铀酰结构基元构筑得到二维（2D）组装体。与之不同的是，无需2,2′-联吡啶即可分离得到异金属三维骨架配合物8([UO₂Cu(L)₂])。固态下测得的发射光谱均呈现典型的铀酰振动精细结构，其分辨率与猝灭程度各有不同，仅配合物7的发射信号来自镍(II)中心。对配合物5、6、8和9的磁性质开展了研究，结果表明，配合物6存在零场分裂效应，配合物9则存在弱反铁磁相互作用。