Isolation and magnetic properties of heterocycle-carrying N-alkoxyarylaminyl radicals

Two N-tert-butoxy-2,6-diaryl-4-(4-pyridyl)phenylaminyls (1) and three N-tert-butoxy-2,6-diaryl-4-(1H-imidazol-1-yl)phenylaminyls (2) were prepared by the reaction of the lithium salts of the corresponding anilines with tert-butyl peroxybenzoate. Although 1 could not be isolated as radical crystals, 2 was successfully obtained as red crystals. The X-ray crystallographic analysis and magnetic susceptibility measurements were performed for one isolated radical.     

Synthesis and properties of naphthalene trimers linked by 1,3,4-oxadiazole spacers

Two types of naphthalene trimers linked by 1,3,4-oxadiazole spacers were synthesized and investigated for their physical and electronic properties. 2,6- and 2,7-isomers on central naphthalene moieties were obtained in the forms of pale yellow solids and colorless crystals, respectively. The melting point of the 2,6-isomer was higher than that of the 2,7-isomer. An X-ray crystallographic analysis revealed a π-stacked column with a short intermolecular distance in the crystals of the 2,6-isomer. The absorption maximum of the 2,6-isomer was red-shifted as compared to that of the 2,7-isomer, indicating a π-conjugation between di-2-naphthyloxadiazole moieties in the 2,6-isomer. The quantum yields of the 2,6- and 2,7-isomers were measured to be 0.97 and 0.74, relative to that of 2,5-di-2-naphthyl-1,3,4-oxadiazole (0.85). Molecular orbital (MO) calculations demonstrated that the 2,6-isomer had a higher electron affinity than the 2,7-isomer. Thus, the crosslinking of building blocks is important for the design of functional materials.     

Syntheses of mixed-ligand tetranuclear gold(I)-nitrogen clusters by ligand exchange reactions with the dinuclear gold(I) formamidinate complex Au(2)(2,6-Me2Ph-form)2

The reaction of the sterically crowded dinuclear gold(I) amidinate complex Au2(2,6-Me2Ph-form)2, 1, with the less bulky bidentate nitrogen ligands results in the formation of tetranuclear gold(I) complexes. When the less bulky amidinate, K(4-MePh-form), A, was reacted with 1 in a 1:1 stoichiometric ratio, crystals containing equal amounts of the tetranuclear and dinuclear gold(I) aryl formamidinates, Au4(4-MePh-form)4 and Au2(2,6-Me2Ph-form)2, where 2,6-Me2Ph-form = B, were found in the same unit cell, 2 x 2THF: space group P, a = 10.794(11) A, b = 14.392(15) A, c = 25.75(3) A, alpha = 82.564(17) degrees, beta = 85.443(18) degrees, gamma = 82.614(19) degrees. The reaction of K(4-MePh-form), A, and 1 in a 1:2 ratio (excess) produced the tetranuclear complex only, 3. The potassium salt of the exchanged bulky ligand, K(2,6-Me2Ph-form), formed as a byproduct. The reaction of the dinuclear gold(I) complex Au2(2,6-Me2Ph-form)2 with the 3,5-diphenylpyrazolate salt, K(3,5-Ph2pz), resulted in the formation of two tetranuclear mixed-ligand complexes, Au4(3,5-Ph2pz)2(2,6-Me2Ph-form)2 x 2THF, 4 x 2THF (space group P21/c, a = 11.5747(19) A, b = 25.497(4) A, c = 21.221(3) A, beta = 96.979(3) degrees) and Au4(3,5-Ph2pz)3(2,6-Me2Ph-form) x THF, 5 x THF (space group P21/c, a = 23.058(5) A, b = 14.314(3) A, c = 18.528(4) A, beta = 90.94(3) degrees. The block crystals from the tetranuclear complex, 4 x 2THF, contain mixed ligands with each pyrazolate ring facing an amidinate ring. The tetranuclear mixed ligand complex, 5 x THF, was isolated as needles with ligands alternating above and below the Au4 plane. The two tetranuclear mixed-ligand complexes emit at 490 and 530 nm, respectively, under UV excitation.     

Synthesis and characterization of 2,6-Dipp(2)-H(3)C(6)SnSnC(6)H(3)-2,6-Dipp(2) (Dipp = C(6)H(3)-2,6-Pr(i)(2)): a tin analogue of an alkyne

The reaction of Sn(Cl)C(6)H(3)-2,6-Dipp(2) (Dipp = C(6)H(3)-2,6-Pr(i)()(2)) with a stoichiometric amount of potassium in benzene affords 2,6-Pr(i)()(2)-H(3)C(6)SnSnC(6)H(3)-2,6-Pr(i)()(2) (1) as dark blue-green crystals. The compound 1 is a tin analogue of an alkyne. It was characterized by (1)H and (13)C NMR and UV-vis spectroscopy, cyclic voltammetry, combustion analysis and X-ray crystallography. The structural data show that 1 has a trans-bent, planar C(ipso)SnSnC(ipso) skeleton with a Sn-Sn bond distance of 2.6675(4) A and a Sn-Sn-C angle of 125.24(7) degrees. The Sn-Sn distance, which is ca. 0.15 A shorter than a conventional Sn-Sn single bond, and the trans-bent structure indicate the presence Sn-Sn multiple bond character unlike the related singly bonded ArPbPbAr species.     

Molecularly nonstoichiometric crystals in phosphorus compounds

Molecularly nonstoichiometric crystals obtained as a result of differential occupation of sites with oxygen atom/phosphorus lone pair of electrons or with sulfur/selenium in three sets of phosphorus compounds are described. These are formed by a combination of (a) [CH2(6-t-Bu-4-MeC6H2O)2]PNMe2 (11) and [CH2(6-t-Bu-4-MeC6H2O)2]P(O)NMe2 (13), (b) [CH2(6-t-Bu-4-MeC6H2O)2]P(S)NMe2 (14) and [CH2(6-t-Bu-4-MeC6H2O)2]P(Se)NMe2 (15), and (c) [(2,6-Me2C6H3O)(O)P-micro-N-t-Bu]2 (16) and (2,6-Me2C6H3O)(O)P(micro-N-t-Bu)2P(O-2,6-Me2C6H3) (17). In the case of c, three different types of crystals with varying stoichiometry of 16 and 17 (1:9, 1:1.5, and 1:0.43) are obtained. The results are substantiated by the combined use of 31P NMR spectroscopy and X-ray crystallography. These observations suggest that we should be cautious with regards to the purity of samples when syntheses involving the oxidation of P(III) systems are reported. It is also emphasized that the apparent P-X distances in some of these crystals cannot actually be taken as true bond lengths.     

Clathrate formation from octaazaphthalocyanines possessing bulky phenoxyl substituents: a new cubic crystal containing solvent-filled, nanoscale voids

The synthesis of octaazaphthalocyanine (AzaPc) derivatives, with bulky phenoxyl substituents placed at eight peripheral positions and containing either H(+), Ni(2+) or Zn(2+) ions in their central cavity, is described. The required precursors, derivatives of pyrazine-2,3-dicarbonitrile, were prepared using a nucleophilic aromatic substitution reaction between 2,6-diisopropylphenol or 2,6-diphenylphenol and 5,6-dichloropyrazine-2,3-dicarbonitrile. Analysis of the resulting AzaPcs by UV/Visible and (1)H NMR spectroscopy confirms that steric isolation of the AzaPc cores was enforced both in solution and in the solid state. X-ray diffraction studies of single crystals of the AzaPcs reveal that solvent inclusion takes place in each case. Of particular significance is the finding that the zinc derivative of 2,3,9,10,16,17,23,24-octa-(2,6-diisopropylphenoxy)octaazaphthalocyanine provides nanoporous cubic crystals, containing massive (8 nm(3)) solvent-filled voids, similar to those of the analogous phthalocyanine derivative. Exchange of the included solvent within the voids can be readily achieved by using a number of alternative solvents including water. Based on the observed loading of included water, the internal volume of this nanoporous cubic crystal appears to be more hydrophilic than its phthalocyanine counterpart.     

The properties of quintet dinitrenes in 2,4,6-triazido-3,5-dichloropyridine crystals

The gamma radiolysis of crystalline 2,4,6-triazido-3,5-dichloropyridine (TACP) was studied by the EPR method. The molecular and crystal structure of TACP was determined by X-ray structure analysis. The prolonged radiolysis of TACP at 77 K caused the appearance of characteristic EPR signals of quintet 2,6-dinitreno-4-azido-3,5-dichloropyridine (2,6-DN) and 2,4-dinitreno-6-azido-3,5-dichloropyridine (2,4-DN). The predominant decomposition of the α-azide groups of TACP was explained by the special features of its molecular and crystal structure. The saturation of the EPR signals of quintet 2,6-DN and 2,4-DN and one-electron radicals with S = 1/2 as the microwave field power increased was studied. The quintet dinitrenes were found to be thermally unstable; they remained in TACP crystals up to 245–250 K.     

Synthesis, spectral, optical and thermal studies of 1-methyl-2,6-dimethyl-4-hydroxypyridinium chloride monohydrate and bromide monohydrate

Semiorganic 1-methyl-2,6-dimethyl-4-hydroxypyridinium chloride monohydrate (MDMPCl.H(2)O) and bromide monohydrate (MDMPBr.H(2)O) salts have been synthesized. Single crystals of MDMPCl.H(2)O and MDMPBr.H(2)O were grown by the slow evaporation method from aqueous solution at constant temperatures 30 and 32 degrees C respectively. The grown crystals were characterized by elemental analysis, FT-IR and FT-NMR techniques and their molecular structures were elucidated. Thermogravimetric, differential thermal analyses and differential scanning calorimetry reveal the presence of water molecules in the crystal lattices and thermal stabilities. Optical transmittance windows in aqueous solution were found as 300-1100 nm using UV-vis-NIR spectrophotometer.     

Supramolecular Assemblies of Three New Metronidazole Derivatives Constructed with Various Dihydroxy-benzoic Acids via Hydrogen Bonds

Metronidazole(MTZ) is an important antibiotic, which has been widely applied to cure protozoal and bacterial diseases for human beings or animals. Herein, three novel drug supramolecular crystals constructed by MTZ with 2,5-dihydroxy-benzoic acid(2,5-DHBA)(1), 2,6-dihydroxy-benzoic acid(2,6-DHBA)(2) and 3,5-dihydroxy-benzoic acid(3,5-DHBA)(3), respectively, have been discovered. The hydrogen bonds of N-H···O(O-H···N), C-H···O and O-H···O play important roles in the 3D supramolecular framework formation for crystals 1-3. Interestingly, due to the vary locations of the substituent groups, the two-dimensional layers in crystals 1 or 2 are constructed via intermolecular hydrogen bonds between MTZ and 2,5-DHBA or 2,6-DHBA, while in crystal 3 water molecules play a significant role except the intermolecular hydrogen bonds between MTZ and 3,5-DHBA. In addition, five synthons of I R₂²(8), II R₃³(9) in crystal 1, III R₁²(4), IV R₂²(8) in crystal 2 and V R₂²(7) in crystal 3 formed through various hydrogen bonds are founded in this work. Systematic studies of syntheses, crystal structures and thermal analysis are reported.     

Reactivity of "Eu(OiPr)2" with phenols: formation of linear Eu3, square pyramidal Eu5, cubic Eu8, and capped cubic Eu9 polymetallic europium complexes

The direct reaction of europium with 2-propanol and phenols has been investigated under a variety of conditions. The reaction of europium metal with 2,6-dimethylphenol and 2,6-diisopropylphenol in 2-propanol at reflux revealed that polymetallic europium complexes could be generated by this method. Hx[Eu8O6(OC6H3Me2-2,6)12(OiPr)8], 1, and H5[Eu5O5(OC6H3iPr2-2,6)6(NCCH3)8], 2, were isolated by recrystallization in the presence of hexanes and acetonitrile, respectively, and characterized by X-ray crystallography. Complex 1 has a cubic arrangement of europium ions with face-bridging mu 4-O donor atoms, edge-bridging mu-O(phenoxide/phenol) ligands, and terminal O(isopropoxide/2-propanol) ligands. Complex 2 is mixed valent and has a square pyramidal europium core with four Eu(II) ions at the basal positions and one Eu(III) ion at the apex. Since these reactions gave complicated mixtures of products from which 1 and 2 could only be obtained in low yields, direct reactions under less forcing reaction conditions were investigated. Europium reacts slowly at room temperature to form arene-soluble divalent [Eu(OiPr)2(THF)x]n, 3. Complex 3 reacts with 2,6-dimethylphenol to form the arene-insoluble complex (H[Eu(OC6H3Me2)2(OiPr)])n, 4. Recrystallization of 4 in the presence of THF results in the crystallographically characterizable divalent trimetallic complex [Eu(OC6H3Me2-2,6)2(THF)2]3, 5, which has an unusual linear metal geometry. In the presence of HOiPr at ambient conditions in the glovebox, crystals of 5 slowly convert to the mixed valent H10[Eu8O8(OC6H3Me2-2,6)10(OiPr)2(THF)6], 6, which was found to have a cubic arrangement of europium atoms similar to 1 by X-ray crystallography. Complex 4, upon heating under vacuum, followed by reaction with THF, forms the arene-soluble divalent complex H18([Eu9O8(OC6H3Me2-2,6)10(THF)7][Eu9O9(OC6H3Me2-2,6)10(THF)6]), 7, which contains two types of capped cubic arrangements of europium ions in the solid state.     

Crystalline photochromism of N-salicylidene-2,6-dialkylanilines: advantage of 2,6-dialkyl substituents of aniline for preparation of photochromic Schiff base crystals

N-(3,5-Dihalosalicylidene)-2,6-dialkylaniline derivatives were prepared and their structure and photochromic properties were investigated. From the X-ray crystallography, it was revealed that steric repulsion between the azomethine hydrogen atom and the alkyl groups at the 2,6-positions of the aniline ring lead to non-planar molecular structure, which was effective for the crystals to exhibit photochromism. The relationship between photochromicity and crystal packing of N-(3,5-dichlorosalicylidene)-2,6-dialkylanilines series was also discussed. The 2,6-dialkylaniline method was suggested to be applicable to the preparation of photochromic Schiff bases with various substituents in the salicylidene rings.     

The Crystal Structures of Pyrazine-2,6-Dicarboxylic Acid DihydRAte and Hexaaquamagnesium(II) Pyrazine-2,6-Dicarboxylate

The crystals of the pyrazine-2,6-dicarboxylic acid dihydrate [C 4 H 2 N 2 (COOH) 2 ]·2H 2 O or H 2 (2,6-PZDC)] crystallize in the monoclinic system, space group C2/m. Their structure is composed of planar layers in which the acid and the water molecules interact via a network of hydrogen bonds. The layers are also hydrogen bonded. Hexaaquamagnesium(II) pyrazine-2,6-dicarboxylate [Mg(H 2 O) 6 ] 2+ [C 4 H 2 N 2 (COO) 2 ] 2 m crystallizes in the monoclinic system, space group P2 1 / n . The magnesium(II) cation is surrounded by six water molecules located at the apices of an almost regular octahedron with the mean Mg-O bond distance of 2.068 Å. The 2,6-PZDC anions are planar and are acceptors in a network of hydrogen bonds donated by the coordinated water molecules.     

4-氨基-2,6-二甲基嘧啶的合成结构和光谱性质研究

合成并制备了氨基嘧啶衍生物C₆H₉N₃的单晶体。用X-射线单晶衍射法测定了晶体结构。测定了分子的红外光谱(400-400Ocm^-1)和紫外可见吸收光谱(190-800nm),探讨了溶剂极性的改变对分子光谱性质的影响。     

Green chemistry strategies using crystal-to-crystal photoreactions: stereoselective synthesis and decarbonylation of trans-alpha,alpha'-dialkenoylcyclohexanones

This paper describes steps to develop green chemistry strategies to prepare compounds with adjacent quaternary centers by stereospecific photodecarbonylation of crystalline ketones bearing radical-stabilizing alkenyl substituents in their alpha-positions. Crystals of trans-2,6-dimethyl-2,6-di(benzyloxycarbonyl-trans-ethenyl)-cyclohexanone, trans-2, prepared by double Michael addition of benzyl propiolate to 2,6-dimethyl-cyclohexanone iso-butylimine (1), were investigated along with those of the dicarboxylic acid (trans-3) and a dibenzylammonium salt derivative (trans-4) to establish the best substrates for the solid-state reaction. While reactions of the ester and the acid lose CO to give radical combination products with high selectivity at low conversions, the crystalline salt gave a similar product in >97% yield. Explorative reactions carried out under sunlight and in semipreparative (1.5 g) scale highlight the potential of reactions in crystals as a viable strategy for the development of green chemistry.     

Synthesis, structure, and bonding of stable dialkylsilaketenimines

Stable (N-aryl)- and (N-alkyl)dialkylsilaketenimines R2SiCNR' [R = 1,1,4,4-tetrakis(trimethylsilyl)butane-1,4-diyl, R' = 2,6-diisopropylphenyl (2a) and 1-adamantyl (2b)] were synthesized as blue and red crystals by the reactions of isolable dialkylsilylene 3 with 2,6-diisopropylphenyl isocyanide and 1-adamantyl isocyanide. X-ray single-crystal analysis disclosed that molecular structures of 2a and 2b were close to each other and were characterized to be allenic rather than zwitterionic or a silylene-isocyanide complex. The bonding characteristics of silaketenimines are found to be affected strongly by the substituents on silicon and nitrogen atoms. Remarkable red-shift of the pi(Si=C) --> pi*(C=N) band of 2a [lambdamax/nm (epsilon) 647(156)] compared with that of 2b [465 nm (109)] is ascribed to lowering of the pi*(C=N) orbital level due to significant interaction between pi*(C=N) and pi*(N-aryl) orbitals.     

七配位二聚体配合物{(PhCH2)2Sn·[2,6-(O2C)2C5H3N](CH3OH)}2的合成及结构

在三乙胺存在下利用三苄基氯化锡和2,6-吡啶二甲酸,以1:1摩尔比反应,合成了七配位二聚体{(PhCH2)2Sn[2,6-(O2C)2C5H3N](CH3OH)}2.通过元素分析、红外光谱和核磁共振氢谱对其结构进行了表征.用X射线单晶衍射法测定了该化合物的晶体结构.化合物为三斜晶系,P1空间群,晶胞参数a=0.9625(6)nm,b=1.0947(9)nm,c=1.996(3)nm,α=90.00(2)°,β=87.69(3)°,γ=90.00(3)°,Z=2,V=2.102(6)nm3,μ=1.248mm-1,F(000)=1000,R1=0.0476,wR2=0.0782.化合物中2个锡原子呈七配位畸变五角双锥构型.生物活性测试结果表明,该化合物具有较强的体外抗肿瘤活性.     

Adaptable Optical Microwaveguides From Mechanically Flexible Crystalline Materials

Flexible organic crystals (elastic and plastic) are important materials for optical waveguides, tunable optoelectronic devices, and photonic integrated circuits. Here, we present highly elastic organic crystals of a Schiff base, 1-((E)-(2,5-dichlorophenylimino)methyl)naphthalen-2-ol ( 1 ), and an azine molecule, 2,4-dibromo-6-((E)-((E)-(2,6-dichlorobenzylidene)hydrazono)methyl)phenol ( 2 ). These microcrystals are highly flexible under external mechanical force, both in the macroscopic and the microscopic regimes. The mechanical flexibility of these crystals arises as a result of weak and dispersive C−H⋅⋅⋅Cl, Cl⋅⋅⋅Cl, Br⋅⋅⋅Br, and π⋅⋅⋅π stacking interactions. Singly and doubly-bent geometries were achieved from their straight shape by a micromechanical approach using the AFM cantilever tip. Crystals of molecules 1 and 2 display a bright-green and red fluorescence (FL), respectively, and selective reabsorption of a part of their FL band. Crystals 1 and 2 exhibit optical-path-dependent low loss emissions at the termini of crystal in their straight and even in extremely bent geometries. Interestingly, the excitation position-dependent optical modes appear in both linear and bent waveguides of crystals 1 and 2 , confirming their light-trapping ability.     

Synthesis of a homoleptic niobium(V) thiolate complex and the preparation of niobium sulfide via thio "sol-gel" and vapor phase thin-film experiments

Reaction of [Nb(NMe(2))(5)] with 10 equiv of 2,6-Me(2)C(6)H(3)SH in toluene results in the formation of red crystals of [Nb(SC(6)H(3)Me(2)-2,6)(5)]. Crystal structure analysis of [Nb(SC(6)H(3)Me(2)-2,6)(5)] showed that the niobium center adopts a distorted trigonal bipyramidal geometry. Niobium disulfide, NbS(2), has been successfully prepared via a thio "sol-gel" process using [Nb(SC(6)H(3)Me(2)-2,6)(5)] as the metal source. In contrast, vapor phase thin-film studies revealed that [Nb(SC(6)H(3)Me(2)-2,6)(5)] functions as a single-source precursor to NbS films.     

Synthesis,crystal, and molecular structures of HIDA and its monomethyl ester

A simple procedure for synthesis of HIDA (2,6-dimethylphenylcarbamoylmethyl iminodiacetic acid) is described. It was obtained in better yield by reaction of 2,6-dimethylphenylcarbamoylmethyl chloride with iminodiacetic acid in carbon tetrachloride. The HIDA (A) was identified by IR and¹H NMR spectroscopy. Two types of crystals were detected in the crystal final product. Since they could be separated, the crystals:A andB were investigated by X-ray analysis. Crystal and molecular structures were solved by direct methods and refined by full-matrix least-squares technique toR=0.047 andR=0.056, respectively. In the structure ofA, the N2 atom is protonated and the molecule exists as a zwitterion. The crystal structure of compoundA is stabilized by strong hydrogen bonds, which are reflected in higher close-packing coefficient, density, and melting point, compared to compoundB. CompoundB is a monomethyl ester of HIDA, which is present as an impurity in the final recrystallized product.     

(Alpha-diimine)chromium complexes: molecular and electronic structures; a combined experimental and density functional theoretical study

Dark brown crystals of [Cr( (1)L) 2] ( 1) were obtained from the reaction of [Cr (III)(acac) 3] (acac (-) = 2,4-pentanedionate) with 2 equiv of 2-methyl-1,4-bis(2,6-dimethylphenyl)-1,4-diaza-1,3-butadiene ( (1)L) and 3 equiv of sodium in tetrahydrofuran (thf) under an Ar atmosphere. Complex 1 possesses an S = 1 ground state, which is attained via intramolecular antiferromagnetic coupling between a high-spin Cr (II) ion ( S Cr = 2) and two anionic alpha-diiminato(1-) ligand pi radicals ( (1)L (*)) (1-). The molecular structure of 1 exhibits a distorted tetrahedral, nearly square-planar geometry. The average C-N imine bond length at 1.346 A is characteristic for the pi radical anion ( (1)L (*)) (1-), and therefore, the electronic structure of 1 is best described as [Cr (II)( (1)L (*)) 2]. This has been confirmed by broken symmetry density functional theoretical calculations BS(4,2) (DFT) at the B3LYP level. The reaction of [Cr (III)(acac) 3] with 1 equiv of 2,3-dimethyl-1,4-bis(2,6-diisopropylphenyl)-1,4-diaza-1,3-butadiene ( (2)L) and 1 equiv of Na in thf under Ar yields red-brown crystals of [Cr (III)( (2)L (*))(acac) 2] ( 2) ( S = 1). The oxidation of 2 with 1 equiv of Fc(PF 6) (Fc (+) = ferrocenium) in CH 2Cl 2 affords crystals of [Cr (III)( (2)L (ox))(acac) 2](PF 6) ( 3) ( S = (3)/ 2). The crystal structure determinations of 2 and 3 revealed that 2 contains a neutral, octahedral Cr (III) species [Cr (III)( (2)L (*))(acac) 2], whereas in 3 the ligand is oxidized, yielding an octahedral monocation [Cr (III)( (2)L (ox))(acac) 2] (+). These electronic structures have been confirmed by DFT calculations.