Hydrothermal synthesis and crystal structures of two novel acentric mixed alkaline earth metal berylloborates Sr3Be2B5O12(OH) and Ba3Be2B5O12(OH)

The synthesis and structure of the isostructural acentric compounds Sr(3)Be(2)B(5)O(12)(OH) (1) and Ba(3)Be(2)B(5)O(12)(OH) (2) are reported for the first time. These compounds crystallize in the space group R3m, and the unit cell parameters are a = 10.277(15) ? and c = 8.484(17) ? for 1 and a = 10.5615(15) ? and c = 8.8574(18) ? for 2. The structures consist of a network of [Be(2)B(4)O(12)(OH)] units interwoven with a network consisting of MO(9) polyhedra (M = Sr, Ba) and BO(3) triangles and exemplify how acentric building blocks such as [BO(3)](3-), [BO(4)](5-), and [BeO(4)](6-) can be especially suitable to build noncentrosymmetric long-range structures. Both networks are centered on the 3-fold rotation axis and present themselves in alternating fashion along [001]. Acentricity is imparted by the alignment of the polarities of BO(3) and BeO(4) environments. Infrared spectroscopy has been used to confirm the local geometries of B and Be, as well as the presence of hydroxide in the crystal structure. Another interesting feature of these compounds is the presence of disorder involving Be and B at the tetrahedral Be site. The degree of the disorder has been confirmed by observing a noticeable shortening of average Be-O bond distances.     

Hydrothermal synthesis and structural characterization of NaLnGeO4 (Ln = Ho, Er, Tb, Tm, Yb, Lu) family of lanthanide germanates

NaLnGeO₄ (Ln = Ho, Tb, Tm, Er, Yb, Lu) were, synthesized in supercritical water, and the products were obtained in quantitative yield as large single crystals. The crystal structures of the family of NaLnGeO₄ were determined, and found to crystallize in the orthorhombic crystal system with the space group Pnma. The structures have olivine type chains as the primary building block, with GeO₄ tetrahedra linking the chains through edge- and corner-sharing with lanthanide octahedral units.     

A class of convolution integral equations involving a generalized polynomial set

The aim of this paper is to derive a solution of a certain class of convolution integral equation of Fredholm type whose kernel involves a generalized polynomial set. Our main result is believed to be general and unified in nature. A number of (known or new) results follow as special cases, simply by specializing the coefficients and parameters involved in the generalized polynomial set. For the sake of illustration, some special cases are mentioned briefly.     

Synthesis and Structural Characterization of K3Th2(PO4)3F2 and RbThPO4F2 as Potential Nuclear Waste Storage Materials

Abstract  

Two new alkali thorium phosphate materials, K₃Th₂(PO₄)₃F₂ and RbThPO₄F₂, were isolated by hydrothermal synthesis at 575 °C. These structures were characterized by single crystal X-ray diffraction using a full-matrix least squares method. The K₃Th₂(PO₄)₃F₂ compound crystallizes in C2/c (No. 15) with a = 15.8179(15) ?, b = 9.8172(8) ?, c = 9.6472(9) ?, β = 121.132(7)°, Z = 4 and R ₁ = 0.0329. This structure contains two large open channels possibly suitable for incorporating radioactive cesium isotopes for waste storage. The RbThPO₄F₂ structure forms in the P2 ₁ /m (No. 11) space group with a = 6.719(4) ?, b = 6.002(3) ?, c = 7.431(5) ?, β = 113.925(19)°, Z = 2 and R ₁ = 0.0359. Unique to this material is a chain of edge sharing thorium with square antiprism coordination environments where fluorine occupies both sites along the edge. Both structures also represent the first occurrences of a fluorinated alkali thorium phosphate material.     

Synthetic approaches to indolo[6,7-a]pyrrolo[3,4-c]carbazoles: potent cyclin D1/CDK4 inhibitors

Synthesis of indolo[6,7-a]pyrrolo[3,4-c]carbazoles 1, a new class of cyclin D1/CDK4 inhibitors, by oxidation of the corresponding aryl indolylmaleimides 2, will be described. Two approaches to the synthesis of 2 were identified that required new methods for the synthesis of 7-substituted indole acetamides 3 and N-methyl (indol-7-yl)oxoacetates 6. The chemistry developed enabled introduction of functionality (-OR, NR(2)) at C(12) and N(13) facilitating structure-activity relationship (SAR) evaluation of this indolocarbazole platform.