CRYSTAL-STRUCTURE AND PHASE-TRANSITION IN THE PEROVSKITE-TYPE LAYER MOLECULAR COMPOSITE NH3(CH2)4NH3PBCL4

The crystal structure of NH3(CH2)4NH3PbCl4 at room temperature (RT pha se) is determined by X-ray diffraction. The structural arrangement is of two-dimensional type, with ammonium alkylene chains located in betw een corner-sharing PbCl6 octahedra layers. The connection between the inorganic and organic parts of the structure is assumed by hydrogen bo nds of N-H ... Cl type. The crystallographic data are: monoclinic, spa ce group P2(1)/c, Z = 4, a = 0.7944(2) nm, b = 0.7772(5) nm, c = 1.976 1(8) nm, beta = 94.84(3)degrees. The organic chain is not centrosymmet rical and shows a left-hand conformation at one extremity. The presenc e of a phase transition is evidenced at T = 323.8 K by calorimetric an d diffraction methods. The crystallographic data of the high-temperatu re phase (HT form) are obtained from single and powder crystal investi gations: monoclinic, space group P2(1)/a, Z = 2, a = 0.7963(5) nm, b = 0.7735(6) nm, c = 1.1011(1) nm, beta = 102.22(9)degrees.