Department of Chemistry, Northwestern University, Evanston, Illinois, 60208-3113, USA.
Inorg Chem. 2010 Sep 20;49(18):8381-8. doi: 10.1021/ic1008895.
The solid-state compounds CsTh(2)Se(6), Rb(0.85)U(1.74)S(6), RbU(2)Se(6), TlU(2)Se(6), Cs(0.88)(La(0.68)U(1.32))Se(6), KNp(2)Se(6), and CsNp(2)Se(6) of the AAn(2)Q(6) family (A = alkali metal or Tl; An = Th, U, Np; Q = S, Se, Te) have been synthesized by high-temperature techniques. All seven crystallize in space group Immm of the orthorhombic system in the KTh(2)Se(6) structure type. Evidence of long-range order and modulation were found in the X-ray diffraction patterns of TlU(2)Se(6) and CsNp(2)Se(6). A 4a × 4b supercell was found for TlU(2)Se(6) whereas a 5a × 5b × 5c supercell was found for CsNp(2)Se(6). All seven compounds exhibit Q-Q interactions and, depending on the radius ratio R(An)/R(A), disorder of the A cation over two sites. The electrical conductivity of RbU(2)Se(6), measured along [100], is 6 × 10(-5) S cm(-1) at 298 K. The interatomic distances, including those in the modulated structure of TlU(2)Se(6), and physical properties suggest the compounds may be formulated as containing tetravalent Th or U, but the formal oxidation state of Np in the modulated structure of CsNp(2)Se(6) is less certain. The actinide contraction from Th to U to Np is apparent in the interatomic distances.
AAn(2)Q(6) 系列的固态化合物 CsTh(2)Se(6)、Rb(0.85)U(1.74)S(6)、RbU(2)Se(6)、TlU(2)Se(6)、Cs(0.88)(La(0.68)U(1.32))Se(6)、KNp(2)Se(6) 和 CsNp(2)Se(6) 均采用高温技术合成。这七种化合物均在正交晶系的 Immm 空间群中，具有 KTh(2)Se(6) 结构类型。在 TlU(2)Se(6) 和 CsNp(2)Se(6) 的 X 射线衍射图中发现了长程有序和调制的证据。TlU(2)Se(6) 存在 4a×4b 超晶格，而 CsNp(2)Se(6) 存在 5a×5b×5c 超晶格。所有七种化合物均表现出 Q-Q 相互作用，并且取决于 An(A) 半径比 R，A 阳离子在两个位置上存在无序。在 298 K 时，沿[100]方向测量的 RbU(2)Se(6) 的电导率为 6×10(-5) S cm(-1)。原子间距离，包括 TlU(2)Se(6) 调制结构中的原子间距离，以及物理性质表明，这些化合物可能含有四价 Th 或 U，但 CsNp(2)Se(6) 调制结构中 Np 的形式氧化态不太确定。从 Th 到 U 再到 Np 的锕系收缩在原子间距离中显而易见。
