Structural diversity and polytypism of lead phenylphosphonates: BING-6 and BING-9

摘要

We report the solvothermal synthesis and characterization of a series of layered lead phenylphosphonates. The crystals were suitable for single crystal X-ray diffraction data, and the two new structures we denote BING-6 [SUNY at Binghamton, Structure No. 6, Pb(PO3C6H5).0.25C(5)H(5)N, triclinic space group P (1) over bar, Z = 2, a = 7.0770(4) Angstrom, b = 9.3113(6) Angstrom, c = 14.6785(g) Angstrom, alpha = 80.456(1)degrees, beta = 78.023(1)degrees, gamma = 73.265(1)degrees] and BING-9 [Pb(PO3-HC6H5)(PO3HC6H4CH3), monoclinic space group C2/c, Z = 4, a = 32.663(8) Angstrom, b = 5.6220(13) Angstrom, c = 8.3307(19) Angstrom, beta = 101.419(4)degrees]. The third structure, a polytype of BING-9, was previously known only from powder X-ray diffraction methods and is denoted 3 [Pb(PO3HC6H5)(2), monoclinic space group C2/c, Z = 4, a = 31.681(6) Angstrom, b = 5.5639(11) Angstrom, c = 8.2515(16) Angstrom, beta = 101.814(4)degrees]. All three structures possess Pb(II) and P centers connected by doubly and triply bridging oxygens. The phenyl groups cap and separate the charge-neutral layers. The phosphonates of BING-6 are nonprotonated, and the structure therefore has a Pb/P ratio of 1:1. Neutral, partially disordered pyridine solvent molecules also reside in the interlamellar space, increasing the layer to layer distance. BING-9 and 3 are polytypes and contain singly protonated phosphonates, for a Pb/P ratio of 1:2. Further characterization methods are discussed, including powder X-ray diffraction, in-situ variable temperature powder X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. Related work in the Ge, Sn, and Mn systems is also discussed. These low-dimensional materials may be useful intercalation compounds for ion-exchange or sensor applications. [References: 40]