Synthesis and crystal structure of a series of incommensurately modulated composite oxohalide compounds

Second-Harmonic-Generation-Active Oxyhalides: CuSb2O3X (X = Cl, Br)

Metal oxyhalides have attracted broad interest recently because of their diverse structures and versatile properties. Here, two oxyhalides, CuSb₂O₃Cl (1) and CuSb₂O₃Br (2), were studied by focusing on their nonlinear-optical properties. They are crystallized in the noncentrosymmetric monoclinic Cc structure, and the layered structures could be derived from a 1:1 combination of CuX- (X = Cl, Br) and Sb₂O₃-type slabs. Their energy gaps were determined to be 2.76 and 2.64 eV. The second-harmonic-generation (SHG) test suggests that they are nonlinear-optical-active, and the effects are ascribed to the contribution of CuX₃O units. Meanwhile, the SbO₃ units' arrangement has a small contribution to the SHG effects. This work is the pioneer SHG investigation of the M^I-M^III-O-X (M^I = Cu, Ag; M^III = trivalent As, Sb, Bi; X = halogen) family.

[NaCl][Cu(HSeO3)2], NaCl-intercalated Cu(HSeO3)2: synthesis, crystal structure and comparison with related compounds

Single crystals of [NaCl][Cu(HSeO3)2] have been prepared by the chemical vapor transport reactions. Its crystal structure (monoclinic, C2/c, a = 13.9874(7), b = 7.2594(4), c = 9.0421(5) Å, β = 127.046(2)°, V = 732.81(7) Å3) is based upon electroneutral [Cu(HSeO3)2] sheets formed by corner sharing between the [CuO4] squares and (HSeO3) groups that are parallel to the (100) plane. Each (SeO2OH)– group forms the Oh1...O2 hydrogen bond to an adjacent hydroselenite group to constitute a [(SeO2OH)2]2– dimer that provides additional stabilization of the copper diselenite sheet. The [Cu(HSeO3)2] sheets alternate with the sheets consisting of zigzag–Na–Cl–Na–Cl–chains formed by Cl atoms and disordered Na sites. The chains are parallel to the c axis. The linkage between the alternating electroneutral [Cu(HSeO3)2] and [NaCl] sheets is provided by the Cu–Cl and Na–O bonds. The coordination of Na is fivefold and consists of three O and two Cl atoms. [NaCl][Cu(HSeO3)2] is a new member of the group of compounds based upon the M(HSeO3)2 layers (M2+ = Cu, Co, Cd). The prototype structure for this group is [Cu(HSeO3)2] that does not have any chemical species separating the copper hydroselenite layers. In other compounds, the interlayer space between the [Cu(HSeO3)2]0 layers is occupied by structural units of different complexity. [NaCl][Cu(HSeO3)2] can be considered as [Cu(HSeO3)2] intercalated with the NaCl layers consisting of one-dimensional–Na–Cl–Na–Cl–chains.