M6[Cd2(CO3)2(B12O18)(OH)6] (M = K, Rb): Borate-Carbonates with Two CdCO3 Embedded in a Cyclic Oxoboron Anion.

Two metal borate-carbonates, M6[Cd2(CO3)2(B12O18)(OH)6] [M = K (1), Rb (2)], were obtained under surfactant-thermal conditions. In 1 and 2, each cyclic [(B12O18)(OH)6]6- anion captures two CdCO3 in two sides of the rings and finally forms the unusual (CdCO3)2@[(B12O18)(OH)6] cluster. Both 1 and 2 show moderate birefringence. Density functional theory calculations indicate that carbonate groups have a major contribution to electron-related optical transition.

Sr2[B5O8(OH)]2 ⋠[B(OH)3] ⋠H2O: A Strontium Borate That Shows Deep-Ultraviolet-Transparent Nonlinear Optical Properties.

A new noncentrosymmetric strontium borate, P1-Sr2[B5O8(OH)]2 ⋅ [B(OH)3] ⋅ H2O (1), has been synthesized under the hydrothermal condition. The P1-Sr2[B5O8(OH)]2 ⋅ [B(OH)3] ⋅ H2O shows a layered B-O network with 9-ring windows in the ab plane. Sr2+ cations, H3BO3, and H2O molecules are located in the voids of layers and interlayers, respectively. The P1-Sr2[B5O8(OH)]2 ⋅ [B(OH)3] ⋅ H2O is the first synthetic phase of veatchite, while the other three polymorphs are found in different natural minerals. This strontium borate is a potential deep-ultraviolet-transparent nonlinear-optical (NLO) crystal whose second-harmonic-generation (SHG) intensity is 1.7 times that of KH2PO4 (KDP) and is phase-matchable. The short wavelength cutoff edge of compound 1 is below 190 nm. Density functional theory (DFT) calculations show that the B-O units are responsible for the nonlinear optical property.

Recent Progress in Crystalline Borates with Edge-Sharing BO4 Tetrahedra.

Crystalline borates have received great attention due to their various structures and wide applications. For a long time, the corner-sharing B-O unit is considered a basic rule in borate structural chemistry. The Dy4B6O15 synthesized under high-pressure is the first oxoborate with edge-sharing [BO4] tetrahedra, while the KZnB3O6 is the first ambient pressure borate with the edge-sharing [BO4] tetrahedra. The edge-sharing connection modes greatly enrich the structural chemistry of borates and are expected to expand new applications in the future. In this review, we summarize the recent progress in crystalline borates with edge-sharing [BO4] tetrahedra. We discuss the synthesis, fundamental building blocks, structural features, and possible applications of these edge-sharing borates. Finally, we also discuss the future perspectives in this field.

Supramolecular hybrids of chiral Waugh polyoxometalate with cyclodextrins.

The development of novel systems for chiral polyoxometalates (POMs) is an attractive research field because of their fascinating topological structures and well-defined functions. Herein, we have developed a new reaction route for the synthesis of two unprecedented chiral Waugh POM-based supramolecular architectures. Single-crystal X-ray diffraction reveals that the architectures exhibit a wavy three-dimensional framework and bamboo-rod-connected framework upon regulating the size of the cyclodextrin and the stacking pattern of the D3 symmetric Waugh {MnMo9}. Solution studies using NMR, circular dichroism and isothermal titration calorimetry corroborate nicely the very weak interactions between the components. The intricate chiral microenvironment originating from the hybrid frameworks may be responsible for the selective recognition of the Λ-{MnMo9} enantiomer. This study highlights the importance of the asymmetric configuration of the POM for designing CD/POM assemblies and understanding their chirality.

Ba2B10O16(OH)2·(H3BO3)(H2O): A Possible Deep-Ultraviolet Nonlinear-Optical Barium Borate.

A new acentric barium borate, Ba2B10O16(OH)2·(H3BO3)(H2O) (1), was synthesized via a hydrothermal process. Compound 1 contains two different boron oxide units of [B5O10(OH)]6- anions and H3BO3 molecules and features 9-ring channels along the c axis in a layered structure. This barium borate is a possible deep-ultraviolet nonlinear-optical crystal for its moderate second-harmonic-generation signal and wide transparency window below 190 nm.

An Ultraviolet Nonlinear Optic Borate with 13-Ring Channels Constructed from Different Building Units.

Under solvothermal conditions, a chair open-framework borate, Na2B9O15(H2O)(H3O) (1), has been synthesized. Compound 1 shows regular pores of zeolites as well as nonlinear optical (NLO) properties of borates. The large 13-ring channels of the boron oxide framework are constructed from different cluster units of B3O7 and B6O13 with three-ring units. The second harmonic generation (SHG) signal intensity of 1 is similar to that of KH2PO4 (KDP) and gradually increased with larger particle size. Compound 1 is a potential UV NLO material for its short wavelength absorption edge.

A density functional theory study of the CH(2)I(2) reaction on Ag(111): Thermodynamics, kinetics, and electronic structures.

Density functional theory calculation was performed to study the adsorption and reaction of CH(2)I(2) on Ag(111). Thermodynamically favorable reactions of CH(2)I(2) on Ag(111) are C-I bond ruptures and CH(2) coupling to form ethylene. The energy barriers for the C-I bond ruptures of chemisorbed CH(2)I(2) on Ag(111) are 0.43-0.48 eV, whereas the activation energy for the C-H bond rupture of chemisorbed CH(2) on Ag(111) is 1.76 eV. The coupling reaction barrier of neighboring chemisorbed CH(2) to form C(2)H(4) on Ag(111) was much less than those of the C-I bond ruptures of CH(2)I(2)(a) and the migration of chemisorbed CH(2) on Ag(111). The adsorption behaviors of different surface species on Ag(111) were well explained in terms of the charge density difference.

Study of absorption spectra and (hyper)polarizabilities of SiC(n) and Si(n)C (n=2-6) clusters using density functional response approach.

We theoretically investigate the absorption spectra, dipole polarizabilities, and first-order hyperpolarizabilities of SiC(n) and Si(n)C (n=2-6) clusters using the density functional response approach. Similar to other semiconductor clusters such as Si and gallium arsenide (GaAs) clusters, the absorption spectra of the SiC(n) and Si(n)C clusters show long absorption tails in the low-transition-energy region and strong absorption peaks in the high-transition-energy region (>4.0 eV). For the same n, the absorption spectrum of the Si(n)C cluster is blueshifted with respect to that of the SiC(n) cluster, which may be related to the larger highest occupied molecular orbital-lowest unoccupied molecular orbital gap in the former. The isotropic (alpha) dipole polarizabilities of the SiC(n) and Si(n)C clusters are larger than the bulk polarizability of 3C-SiC and lie between the dipole polarizabilities of Si and C. The SiC(n) clusters have lower dipole polarizabilities and larger first-order hyperpolarizabilities than the Si(n)C clusters. The size dependence of the first-order hyperpolarizabilities of the SiC(n) clusters, which have approximate Si-terminated linear chain geometry, is similar to that observed in pi-conjugated organic molecules.

Poly[mu-aqua-mu4-naphthalene-1,8-dicarboxylato-zinc(II)].

In the title complex, [Zn(C(12)H(6)O(4))(H(2)O)](n), a Zn(II) polymer based on naphthalene-1,8-dicarboxylate (1,8-nap), the Zn(II) atoms adopt an elongated octahedral coordination geometry. A zigzag chain is formed by mu(2)-aqua ligands and mu(2)-carboxylate groups of the 1,8-nap ligands. Adjacent parallel chains are further linked by 1,8-nap ligands, forming a twisted two-dimensional layer structure along the (100) plane.

Theoretical study of two-photon absorption in donor-acceptor chromophores tetraalkylammonium halide/carbon tetrabromide.

Two-photon absorption properties of a series of donor-acceptor chromophores of tetraalkylammonium halide/carbon tetrabromide ([NR4h.CBr4], h = Cl, Br, I; R = Me, Et, Pr) complexes are investigated in terms of the calculated results by the time-dependent density functional theory (TDDFT) technique combined with the sum-over-states (SOS) method. The modeling two-photon absorption spectra show that these charge-transfer complexes have large two-photon absorption (TPA) cross sections and the [NEt4I.CBr4] has the largest TPA cross section delta with the value of 5.0 x 10(-45) cm4 s photon(-1). The maximum values of delta increase with increasing separations between the donor/acceptor in the order Cl...Br < Br...Br < I...Br for [NEt4h.CBr4] complexes; however, the TPA cross sections delta vary slightly as the size of the alkyl group increases from methyl to propyl for the bromide as a donor, and the maximum wavelength of the TPA peak lambdamax indicates a bathochromic shift. The charge transfers from the halide anion to the carbon tetrabromide make a significant contribution to the excited states, and the donor-acceptor charge transfer plays an important role in the TPA activity, whereas changes in size of alkyl group do not make a substantial contribution to TPA.