Pei-Xin Li

Synthesis, crystal structures, and luminescent properties of two series' of new lanthanide (III) amino-carboxylate-phosphonates.

Hydrothermal reactions of lanthanide(III) chlorides with 4-HOOC-C(6)H(4)-CH(2)NHCH(2)PO(3)H(2) (H(3)L) at different ligand-to-metal (L/M) ratios afforded nine new lanthanide(III) carboxylate-phosphonates with two types of 3D network structures, namely, LnCl(HL)(H(2)O)(2) (Ln = Sm, 1; Eu, 2; Gd, 3; Tb, 4; Dy, 5; Er, 6) and [Ln(2)(HL)(H(2)L)(L)(H(2)O)(2)].4H(2)O (Ln = Nd, 7; Sm, 8; Eu, 9). Compounds 1-6 are isostructural and feature a 3D network in which the LnO(7)Cl polyhedra are interconnected by bridging CPO(3) tetrahedra into 2D inorganic layers parallel to the bc plane. These layers are further cross-linked by organic groups of the carboxylate-phosphonate ligands via the coordination of the carboxylate groups into a pillared-layered architecture. Compounds 7-9 are also isostructural and feature a 3D open-framework composed of 1D lanthanide(III) phosphonate inorganic slabs which are further bridged by organic groups of the carboxylate-phosphonate liagnds via the coordination of the carboxylate groups, forming large 1D tunnels along the b-axis which are filled by lattice water molecules. Luminescent measurements indicate that compounds 2, 4, and 5 show strong emission bands in red, green, and yellow light region, respectively. Magnetic properties of 2, 3, 5, and 7 have also been studied.

A Series of New Phases Containing Three Different Asymmetric Building Units

Systematic explorations of the new phases in the Pb(II)/Bi(III)-TM(d(0)/d(1))-Se(IV)-O systems by hydrothermal syntheses led to five new quaternary phases whose structures are composed of three different asymmetric building units, namely, Pb(2)V(V)(2)Se(2)O(11) (1), Pb(2)V(IV)(3)Se(5)O(18) (2), Pb(2)Nb(V)(2)Se(4)O(15) (3), Bi(2)V(V)(2)Se(4)O(16) (4), and Bi(2)Mo(VI)(2)Se(2)O(13) (5). The structure of 1 features a 3D network built by 1D anionic chains of [V(2)O(5)(SeO(3))(2)](4-) interconnected by Pb(2+) ions with six-membered-ring (MR) tunnels along the b axis. The structure of 2 features a 3D anionic framework composed of V(IV)O(6) octahedra corner-sharing with SeO(3) anions, with the Pb(2+) ions located at the resultant 8-MR tunnels. The oxidation state of the vanadium cation is 4+ due to the partial oxidation of V(2)O(3) by SeO(2) at high temperature. The structure of 3 features novel 1D double chains of [Nb(2)O(3)(SeO(3))(4)](4-) that are interconnected by Pb(2+) ions, forming a 3D network with 12-MR tunnels along the c axis. 4 features a 3D framework composed of 2D layers of [Bi(2)(SeO(3))(2)](2+) and 1D [(VO(2))(2)(SeO(3))(2)](2-) double chains. The structure of 5 features a 3D network composed of bismuth(III) selenite with large 10-MR tunnels along the a axis that are occupied by Mo(2)O(10) dimers. The results of optical diffuse-reflectance spectrum measurements and electronic structure calculations based on density functional theory methods indicate that all five compounds are wide-band-gap semiconductors. Luminescent property measurements for compounds 1-5 and magnetic measurements for compound 2 were also made.

Explorations of New Second-Order Nonlinear Optical Materials in the K-I-M-II -I-V-O Systems

Explorations of new second-order nonlinear optical (NLO) materials in the K(I)-M(II) -I(V)-O systems led to four novel mixed metal iodates, namely, K(2)M(IO(3))(4)(H(2)O)(2) (M = Mn, Co, Zn, Mg). The four compounds are isostructural and crystallize in space group I2 which is in the chiral and polar crystal class 2. Their structure features zero-dimensional {M(IO(3))(4)(H(2)O)(2)}(2-) anions that are separated by K(+) cations. The M(II) centers are ligated by two aqua ligands in trans fashion and four monodentate iodate anions. The K(+) cation is eight-coordinated by two iodate anions in bidentate chelating fashion and four other iodates in a unidentate fashion. Second harmonic generation (SHG) measurements indicate that K(2)Zn(IO(3))(4)(H(2)O)(2) and K(2)Mg(IO(3))(4)(H(2)O)(2) display moderate SHG responses that are approximately 2.3 and 1.4 times of KH(2)PO(4) (KDP), respectively, and they are also phase-matchable. The SHG response of K(2)Co(IO(3))(4)(H(2)O)(2) is much weaker (about 0.3 x KDP), and no obvious SHG signal was detected for K(2)Mn(IO(3))(4)(H(2)O)(2). Results of optical property calculations for the Zn and Mg phases revealed SHG responses of approximately 5.3 and 4.7 times of KDP, respectively, the order of Zn > Mg is in good agreement with the experiment data.

New types of 3D organically templated Zn2+/Cd2+-Cu+ mixed metal sulfites.

Two types of new organically templated mixed-metal sulfites, namely, [H(2)pip][NaZn(2)Cu(SO(3))(4)] (1) and [H(2)pip][CdCu(4)(SO(3))(4)] (2) (pip = piperazine), have been synthesized under hydrothermal conditions and structurally characterized. Both compounds exhibit a novel 3D mixed-metal inorganic framework with organic template molecules occupying the tunnels of the inorganic skeleton. Compound 1 features a 2D Zn(2)Cu(SO(3))(4)(3-) layer parallel to the ac plane in which the 1D chains of Zn(SO(3))(2)(2-) anions along the c axis are interconnected with the Cu(+) ions via Cu-S bonds. Neighboring Zn(2)Cu(SO(3))(4)(3-) layers are further interconnected by bridging Na(+) ions via Na-O-S bonds into a 3D network, forming 1D tunnels along the a axis which are occupied by the doubly protonated piperazine cations. Compounds 2 features a novel 3D inorganic framework of CdCu(4)(SO(3))(4)(2-) with 2D layers based on Cu(4)(SO(3))(4)(4-) cubanelike clusters. The cluster layers are further interconnected by Cd(II) ions, forming 1D tunnels of eight-membered rings along the c axis in which the piperazine template cations are located. Luminescent property measurements as well as band structure calculations based on density functional theory methods were also made.