Hexa boron-dipyrromethene cyclotriphosphazenes: synthesis, crystal structure, and photophysical properties

We have synthesized four examples of a cyclotriphosphazene ring appended with six boron-dipyrromethene dyes N(3)P(3)(BODIPY)(6) by adopting two different methods. In method I, 1 equiv of N(3)P(3)Cl(6) was treated with 6 equiv of meso-(o- or m- or p-hydroxyphenyl)boron-dipyrromethene in tetrahydrofuran (THF) in the presence of cesium carbonate. This afforded N(3)P(3)(BODIPY)(6) in yields ranging from 80 to 90%. In method II, we first prepared hexakis(p-formylphenoxy)cyclotriphosphazene N(3)P(3)(CHO)(6) by treating 1 equiv of N(3)P(3)Cl(6) with 6 equiv of 4-hydroxybenzaldehyde in the presence of cesium carbonate in THF. In the second step, N(3)P(3)(CHO)(6) was condensed with excess of pyrrole in the presence of catalytic amount of trifluoroacetic acid (TFA) in CH(2)Cl(2) at room temperature and afforded hexakis(p-phenoxy dipyrromethane)cyclotriphosphazene. In the last step, the hexakis(p-phenoxy dipyrromethane)cyclotriphosphazene was first oxidized with 6 equiv of DDQ in CH(2)Cl(2) at room temperature for 1 h followed by neutralization with triethylamine and further reaction with excess BF(3)·Et(2)O afforded the target N(3)P(3)(BODIPY)(6) in 16% yield. The route II was used only for the synthesis of one target compound whereas the route I was used for the synthesis of all four target compounds. The four compounds were characterized by mass, NMR, absorption, electrochemical, and fluorescence techniques. The crystal structure solved for one of the compounds revealed that the P(3)N(3) ring is slightly puckered and the six substituents were not interacting with each other and attained pseudo-axial and pseudo-equatorial positions. The photophysical studies in five different solvents indicated that the compounds exhibit large Stokes' shifts unlike reference monomeric BODIPYs indicating that the compounds are promising for fluorescence bioassays. The quantum yields and lifetimes of compounds 1-4 depends on the type of BODIPY unit attached to the cyclotriphosphazene ring.     

Allyl strontium compounds: synthesis, molecular structure and properties

The synthesis and attempted isolation of neutral bis(allyl)strontium [Sr(C(3)H(5))(2)] (1) resulted in the isolation of potassium tris(allyl)strontiate K[Sr(C(3)H(5))(3)] (2). In situ generated 1 shows a pronounced Br?nsted basicity, inducing polymerisation of THF. Ate complex 2 crystallises as [K(THF)(2){Sr(C(3)H(5))(3)}(THF)](∞) (2·(THF)(3)). The salt-like solid state structure of 2·(THF)(3) comprises a two-dimensional network of (μ(2)-η(3):η(3)-C(3)H(5))(-) bridged potassium and strontium centres. Synthesis of allyl complexes 1 and 2 utilised SrI(2), [Sr(TMDS)(2)] (3) (TMDS = tetramethyldisilazanide), and [Sr(HMDS)(2)] (HMDS = hexamethyldisilazanide) as strontium precursors. The solid state structure of previously reported [Sr(TMDS)(2)] (3) was established by X-ray single crystal analysis as a dissymmetric dimer of [Sr(2)(TMDS)(4)(THF)(3)] (3·(THF)(3)) with multiple Si-HSr agostic interactions. The presence of ether ligands (THF, 18-crown-6) influenced the Si-HSr resonances in the NMR spectra of the amido complex 3.     

Microwave synthesis,structure, and properties of molybdophosphate compounds

Two compounds of disphosphopentamolybdate(VI) with the formulae (C₄H₁₄N₂O)₃- [P₂Mo₅O₂₃]?·?3H₂O (1) and (C₄H₁₄N₂O)₅(NH₄)₂[P₂Mo₅O₂₃]₂?·?5H₂O (2) have been synthesized by a simple, fast and efficient microwave method, and their crystal structures and spectroscopic properties have been studied. The heteropoly anion [P₂Mo₅O₂₃]^6? has a known structure built of five MoO₆ octahedra and two PO₄ tetrahedra. The MoO₆ octahedra form a pentagonal ring by sharing four edges and one corner and the PO₄ tetrahedra are attached to one side of the ring by three oxygen atoms. The most interesting feature of compound 1 is its extensive framework based on a one-dimensional zigzag chain. In compound 2, a more extensive and complicated framework of hydrogen bonds joins the anions, organic cations and water molecules together.     

Synthesis, structure and properties of pyrazole type tetrakis compounds

A series of pyrazole type tetrakis compounds has been synthesized by reaction of aromatic or heterocyclic dialdehydes and pyrazolone derivatives. Structure and tautomerism of the products were investigated by spectroscopic methods and X-ray analysis. Several tetrakis compounds form inclusion complexes with solvents like alcohols, ethers, and ketones in a definite ratio via hydrogen bonds.     

One-pot synthesis of Schiff-base-containing Ni8 clusters: solvothermal synthesis, structure, and magnetic properties

Solvothermal in situ generation of a Schiff-base ligand (L) in the presence NiCl(2) and trimesic acid (H(3)BTC) in ethanol resulted in clusters, Ni(8)(L)(4)Cl(8).(H(2)O)(0.5), consisting of three different coordination geometries, four paramagnetic and four diamagnetic Ni(II), exhibiting both ferromagnetic and antiferromagnetic exchange interactions.     

Cu4Mo6Se8: synthesis, crystal structure, and electronic structure of a new Chevrel phase structure type

Cu4Mo6Se8 has been synthesized by intercalation of Cu into Cu2Mo6Se8 at room temperature, and its crystal structure has been determined. This compound crystallizes in the triclinic space group P, with a = 6.7609(8) A, b = 6.8122(7) A, c = 7.9355(10) A, alpha = 70.739(4) degrees , beta = 72.669(4) degrees , gamma = 84.555(5) degrees , and Z = 1. Instead of residing in the voids between corners or edges of Mo6Se8 clusters as in the classic R Chevrel structure, the Cu atoms in Cu4Mo6Se8 fully occupy four sites between faces of two adjacent Mo6Se8 clusters. Thus, two of the six Mo atoms in each cluster do not have capping Se atoms from neighboring clusters. This represents a new triclinic structure type for Chevrel phases. In addition to the synthesis and crystal structure, we present and discuss results from electronic structure calculations using both extended Hückel and density functional theory. These calculations predict Cu4Mo6Se8 to be metallic. We also report results from Cu intercalation into Chevrel phase sulfides and tellurides. Preliminary experiments suggest that a telluride analogue of Cu4Mo6Se8 exists.     

Nitridoborates of the lanthanides: synthesis,structure principles,and properties of a new class of compounds

Investigations of the nitridoborates of lanthanides (Ln) have progressed significantly during the last few years. New compounds have been synthesized and characterized and are presented here together with some of their properties. Currently two distinct methods serve for the preparation of nitridoborate compounds; either hexagonal boron nitride undergoes a fragmentation through the reaction with LnN, or dinitridoborate ions are converted into other nitridoborate ions. Lanthanide nitridoborates contain molecular anions such as [BN]n-, [BN2]3-, [B2N4]8-, [B3N6]9-, and [BN3]6- which may occur in combinations with other nitridoborates or with additional nitride ions. In crystal structures of lanthanide nitridoborates these anions are arranged in layers and are surrounded by metal atoms in a characteristic fashion. Terminal N atoms are capped by metal atoms forming a square-pyramid, and B atoms prefer a trigonal-prismatic environment of metal atoms. Nitridoborates form saltlike as well as metal-rich compounds and have the potential to show a lot of what are considered to be important solid-state properties, thus they have a good chance to establish their position within the group of relevant materials.     

7-Pyridylindoles: synthesis, structure, and properties

A series of three isomeric 7-pyridylindoles (7-PIs) are prepared where the pyridine attachment is through C2, C3, or C4. These systems are prepared by a combination of the Bartoli reaction and the Stille coupling with an appropriate pyridyl stannane. By treatment with CH(3)I, the 7-PIs can be converted to their pyridinium salts. Deprotonation at the NH of these salts leads to a zwitterion which, in the 4-pyridyl system, also exists as a neutral isomer. The photophysical and NMR properties of these systems are discussed. All three pyridylindoles are analyzed by X-ray crystallography and shown to exist in different states of aggregation dictated by the formation of intra- and intermolecular H-bonds.     

Multiethynyl corannulenes: synthesis, structure, and properties

Syntheses, crystal structures, ab initio density functional theory computations, and photophysical properties of 1,6-di-, 1,2,5,6-tetra-, and 1,3,5,7,9-pentaethynyl-substituted corannulenes (classes 3, 4, and 5, respectively) are reported. Classes 3 and 4 were prepared from the corresponding corannulenyl bromides and terminal alkynes in excellent yields (nine examples, with yields of 57-92%) using the Sonogarshira reaction. Class 5 was prepared from 1,3,5,7,9-pentacholorocorannulene and trimethylalkynylstannanes using a modification of Nolan's procedure (8 examples, with yields of 45-93%). The molecular packing in crystals of 1,6-diphenylethynyl-2,5-dimethylcorannulene (3-Ph2) displays a polar columnar structure with all of the molecule bowls oriented in the same direction. Similarly, 1,2,5,6-tetrakis(3,5-dimethylphenylethynyl)corannulene [4-Ar(c)5] and 1,3,5,7,9-pentakis(3,5-dimethylphenylethynyl)corannulene [5-Ar(c)5] form columnar structures, but the bowls are oriented in opposing directions. Additionally, the number of attached alkynyl arms is correlated with an increase in bowl depth of the corrannulene nucleus. Most of the aryl derivatives displayed high-quantum-efficiency solution luminescence and variable emission wavelengths that were dependent on the nature of the substitution.     

New dispiro compounds: synthesis and properties

We report the synthesis and structural characterization of two dispiro compounds. These two positional isomers have been designed and synthesized through an efficient method. Because of the rigidity and orthogonality of the spiro bridge, both molecules exhibit a well-defined architecture which consists of two fluorene rings connecting to an indenofluorenyl unit via two sp3 carbon atoms. The structural, electrochemical, optical, and thermal properties of these dispiro isomers are discussed.     

Uranyl heteropolyoxometalate: synthesis, structure, and spectroscopic properties

A novel uranium heteropolyoxometalate, [H(3)O](4)[Ni(H(2)O)(3)](4){Ni[(UO(2))(PO(3)C(6)H(4)CO(2))](3)(PO(4)H)}(4)·2.72H(2)O, has been prepared under mild hydrothermal conditions using the diethyl(2-ethoxycarbonylphenyl)phosphonate ligand and in situ ligand synthesis of the HPO(4)(2-) anion. The cluster is derived from a common UO(7), pentagonal bipyramid and is constructed by employing nickel(II) metal ions as linkers. The 3d-5f heteropolyoxometalate core incorporates 12 classical pentagonal uranyl groups and four Ni(2+) octahedral units.     

Molecular optical switches: synthesis, structure, and photoluminescence of spirosila compounds

Starting from a silicon dichloro substituted silole and a silacyclobutene, a series of new organosilicon-based spiro compounds was synthesized by using standard organometallic reaction procedures. The spiro compounds that combine two organic photoactive subunits at one silicon center were fully characterized by the usual analytical and spectroscopic methods, which include molecular structure determination by single-crystal X-ray analysis. Photoluminescence spectra of the compounds were recorded in the solid state and also as dilute solutions in THF. Interpretation of the spectra revealed that photoluminescence in this series of compounds originated from the stilbene or its vinylogue subunits. Different linkages of these groups to the silicon atoms (cyclic or open structures, four- or five-membered cycles) strongly affected both the excitation and the emission spectra, which show different emission maxima depending on the state of the sample (solid state or in solution) and the wavelength of light used for excitation. Thus, owing to their optoelectronic properties these compounds might be useful tools for the design of sensitive sensor materials and of optical switches.     

Starburst substituted hexaazatriphenylene compounds: synthesis, photophysical and electrochemical properties

Starburst-substituted hexaazatriphenylene compounds have been designed and synthesized by introducing various peripheral aryl substituents to the central heterocyclic core. The effects of various substituent groups on the photophysical and electrochemical properties of the substituted hexaazatriphenylene have been investigated. Significant red-shifts of the absorption peak (from 413 nm to 530 nm) and emission peak (from 432 nm to 700 nm) were observed when the electron-donating ability of the aryl substituents was increased, corresponding to a decrease in the band gap from 2.90 eV to 2.05 eV. Introducing bulky substituents with weak electron-donating ability enhances the fluorescence quantum yield from 23% to 87%. In contrast, incorporating aryl substituents with strong electron-donating ability decreases the fluorescence quantum yield. Also, due to the extended conjugation between the aryl substituents and the hexaazatriphenylene core, the reduction potentials of the compounds were reduced and the LUMO levels were thus increased.     

Tin-chalcogen double-bond compounds, stannanethione and stannaneselone: synthesis, structure, and reactivities

The first isolation of diarylstannanethione (tin-sulfur double-bond compound) and diarylstannaneselone (tin-selenium double-bond compound), Tbt(Ditp)Sn=X (Tbt = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl; Ditp = 2,2' '-diisopropyl-m-terphenyl-2'-yl; X = S and Se) was accomplished by dechalcogenation of the corresponding highly hindered tetrachalcogenastannolanes, Tbt(Ditp)SnX(4). The (119)Sn NMR of stannanethione, Tbt(Ditp)Sn=S, and stannaneselone, Tbt(Ditp)Sn=Se, showed only one low-field broad signal at 531 and 440 ppm, respectively, characteristic of a tricoordinated tin, and hence, the stannanethione and stannaneselone display an intrinsic nature of tin-chalcogen double-bond compounds. The X-ray crystallographic analysis of the isolated stannaneselone, Tbt(Ditp)Sn=Se 5a, revealed a completely trigonal geometry around the central tin with a remarkably short Sn-Se bond length, indicative of structural similarity to a ketone.     

Deprotonative metalation using ate compounds: synergy, synthesis, and structure building

Historically, single-metal organometallic species such as organolithium compounds have been the reagents of choice in synthetic organic chemistry for performing deprotonation reactions. Over the past few years, a complementary new class of metalating agents has started to emerge. Owing to a variable central metal (magnesium, zinc, or aluminum), variable ligands (both in their nature and number), and a variable second metallic center (an alkali metal such as lithium or sodium), "ate" complexes are highly versatile bases that exhibit a synergic chemistry which cannot be replicated by the homometallic magnesium, zinc, or aluminum compounds on their own. Deprotonation accomplished by using these organometallic ate complexes has opened up new perspectives in organic chemistry with unprecedented reactivities and sometimes unusual and unpredictable regioselectivities.     

Monoammoniate of calcium amidoborane: synthesis, structure, and hydrogen-storage properties

The monoammoniate of calcium amidoborane, Ca(NH(2)BH(3))(2)·NH(3), was synthesized by ball milling an equimolar mixture of CaNH and AB. Its crystal structure has been determined and was found to contain a dihydrogen-bonded network. Thermal decomposition under an open-system begins with the evolution of about 1 equivalent/formula unit (equiv.) of NH(3) at temperatures <100 °C followed by the decomposition of Ca(NH(2)BH(3))(2) to release hydrogen. In a closed-system thermal decomposition process, hydrogen is liberated in two stages, at about 70 and 180 °C, with the first stage corresponding to an exothermic process. It has been found that the presence of the coordinated NH(3) has induced the dehydrogenation to occur at low temperature. At the end of the dehydrogenation, about 6 equiv. (～ 10.2 wt %) of hydrogen can be released, giving rise to the formation of CaB(2)N(3)H.     

New organophosphorus compounds containing nicotinamide: synthesis,structure and DFT calculations

Novel organophosphorus compounds, containing Nicotinamide, with formula C₅H₄NC(O)NHP(O)R₂, R=Cl (1), OH (2), N(C₂H₅)₂ (3), N(C₃H₇)₂ (4), N(n-C₄H₉)₂ (5), NHC₃H₅ (6), NHC₅H₉ (7), were synthesized and characterized by ¹H, ¹³C, ³¹P, NMR, IR, spectroscopy and elemental analysis. Single crystal structures of 3 7 were determined by X-ray crystallography. ¹HNMR spectra of compounds 2, 3, 6–8 demonstrated interesting long-range coupling constant, ⁿ J _P,H (n = 5 7). Crystallographic data revealed that in both molecules 3 and 7, the phosphoryl and the carbonyl groups have anti-configurations and the phosphorus atoms in these structures have distorted tetrahedral configuration. All the hydrogen bonds and electrostatic interactions make a three dimensional polymeric network for both 3 and 7. Interestingly, two independent conformers were detected in the unit cell of compound 7. The two conformers of the title compound can be observed in a solid phase but only one compound defined in a solution. These two conformers are connected to each other by a short contact, N (amine)···H–C (pyridine) with 2.626 Å distance. The molecular geometry of 7 was calculated by DFT/B3LYP (6–31+G**) quantum chemical calculations. The computational optimized geometric parameters and vibrational frequencies showed a good agreement with the experimental results, considering reasonable variations arising from the differences between solid and gaseous phases. Theoretical calculations revealed that the more stable conformer of the title compound is conformer 1 with the energy of ?1335.723996 a.u., which is about 1.17 kcal/mol lower than the energy of conformer 2.