β-硝基-5,10,15,20-四(2-甲氧基苯基)卟啉合成及其阻旋异构

在采用区域选择性硝化方法合成β-硝基-5,10,15,20-四芳基卟啉铜、镍配合物的过程中,发现并通过核磁等方法分析了5,10,15,20-四(2-甲氧基苯基)卟啉及其相应β-硝基取代物的阻旋异构现象.图谱分析表明,与其结构类似的5,10,15,20-四(2-羟基苯基)卟啉及5,10,15,20-四(4-甲氧基苯基)卟啉系列化合物没有该阻旋异构现象,说明邻位甲氧基阻碍了苯环与芳环之间C-C单键的旋转.进一步通过Chemdraw 3D Ultra软件能量最小化计算,讨论了阻转异构体可能的方式.     

卟啉化合物的研究 XIX: 四苯基卟啉Schiff碱的合成和卟啉蒽醌Schiff碱的光物理性质

用Vilsmeier醛基化反应的中间物直接胺解制备四苯基卟啉Schiff碱, 测定了四苯基卟啉蒽醌Schiff碱(P-AQ)在光照和氩气氛中的可见光谱差谱(光-暗)和荧光光谱。对结果进行了讨论, 并用在光辐照下P-AQ分子构型变化来解释分子内电子转移生成P^+.-AQ^-. 离子自由基的稳定性。     

卟啉化合物的研究 XIX: 四苯基卟啉Schiff碱的合成和卟啉蒽醌Schiff碱的光物理性质

用Vilsmeier醛基化反应的中间物直接胺解制备四苯基卟啉Schiff碱, 测定了四苯基卟啉蒽醌Schiff碱(P-AQ)在光照和氩气氛中的可见光谱差谱(光-暗)和荧光光谱。对结果进行了讨论, 并用在光辐照下P-AQ分子构型变化来解释分子内电子转移生成P^+.-AQ^-. 离子自由基的稳定性。     

卟啉化合物的研究 ⅪⅩ.四苯基卟啉Schiff碱的合成和卟啉蒽醌Schiff碱的光物理性质

用Vilsmeier醛基化反应的中间物直接胺解制备四苯基卟啉Schiff碱,测定了四苯基卟啉蒽醌Sohiff碱(P-AQ)在光照和氩气氛中的可见光谱差谱(光—暗)和荧光光谱。对结果进行了讨论,并用在光辐照下P-AQ分子构型变化来解释分子内电子转移生成P_-AQ_离子自由基的稳定性。     

meso,β-和β,β-全氟醚基磺酸酯桥连双卟啉的合成

β-氟砜基全氟醚基取代四芳基卟啉与5-(4-羟苯基)-10,15,20-三苯基卟啉、BINOL反应分别生成meso,β-和β,β-全氟醚基磺酸酯桥连双卟啉,双卟啉与醋酸锌在CHCl₃/CH₃OH中回流可高产率获得双锌卟啉,测定并讨论了meso,β-和β,β-全氟醚基磺酸酯连接双卟啉的紫外可见和荧光光谱.     

双(对-氨基苯基)-2,3,7,8,12,13,17,18-八甲基卟啉及其金属衍生物的合成与表征

从3-甲基-2,4-戊二酮出发,经多步反应合成了3,3′,4,4′-四-甲基-2,2′-二吡咯基甲烷(TMDPM),改进了合成TMDPM的脱羧反应.研究了TMDPM与对-硝基苯甲醛反应合成meso-5,15-双-苯基-卟啉反应,发现对-甲基苯磺酸是卟啉原合成的良好催化剂,2,3-二-氯-5,6二氰基-1,4-苯醌是将卟啉原转化为卟啉的良好氧化剂;硝基卟啉经SnCl₂还原成氨基卟啉后,用固-液抽提进行氨基卟啉的纯化,得到了5,15-双(对-硝基苯基)-2,3,7,8,12,13,17,18-八甲基卟啉、5,15-双(对-氨基苯基)-2,3,7,8,12,13,17,18-八甲基卟啉及其金属衍生物,并表征了其结构     

稀土乙酰丙酮-α,β,γ,δ-四邻硝基苯基卟啉钬的合成

本文首次合成出镧系乙酰丙酮-α,β,γ,δ-四邻硝基苯基卟啉配合物Ho(o-NO_2)TPPacac(Ⅰ),并简单地讨论了它的性质。 反应中间物三水乙酰丙酮配合物Ho(acac)_3·3H_2O用文献方法[1]合成和纯制。α,β,γ,δ-四邻硝基苯基卟啉(o-NO_2)TPP用改进的Kim,J.B.法[2]     

Mn(Ⅲ)-四芳基卟啉与高碘酸四丁基铵催化羧酸的氧化脱羧:金属、取代基和轴向阴离子配体的影响

锰四芳基卟啉与高碘酸四丁基铵(n-Bu4NIO4)和咪唑(ImH)组合,为羧酸氧化脱羧提供了一个有效的催化剂体系.中位含有吸电子基团和/或大体积芳基的中位-四芳基卟啉使金属卟啉的活性降低.咪唑的存在和金属中心的选择对金属卟啉的催化性能起关键性作用,催化体系中的反离子也有重要影响.Mn(TPP)CN/n-Bu4NIO4/ImH体系的催化活性最好.二苯基乙酸的氧化脱羧可能涉及高价的含氧锰物种与反应物间的相互作用,提出了可能的反应机理.     

新型2-氢醌-多羟基卟啉的合成及其抗菌活性研究

为寻找新的光动力治疗光敏剂,首次利用电中性的对苯二酚与2-硝基-5,10,15,20-四芳基卟啉直接反应,制备了一系列新型2-氢醌-5,10,15,20-四(4-羟基苯基)卟啉,分离产率达90%以上.用青霉素钠做对照,首次研究了2-氢醌-5,10,15,20-四(4-羟基苯基)卟啉及其Ni(Ⅱ),Zn(Ⅱ)配合物对金黄色葡萄球菌(Staphylococcus aureus,ATCC 25923)和大肠杆菌(Escherichia coli,ATCC 25922)的抑菌活性,显示其浓度为80μmol/L时,就能完全抑制金黄色葡萄球菌的生长(而相应的青霉素钠的浓度为320μmol/L),但对大肠杆菌的作用不明显.结果表明,2-氢醌-5,10,15,20-四(4-羟基苯基)卟啉及其金属配合物在杀灭金黄色葡萄球菌等方面具有很好的应用前景.     

meso-四(间烷氧基苯基)卟啉及其金属配合物的合成、表征和液晶性能研究

1987年Gregg等[1]合成了八酯取代卟啉及其Zn配合物并研究了其液晶性,1990年Shimichi等[2]报道了对-烷氧取代型四苯基卟啉(n=10,12)及其Co,Zn配合物(n=10)的液晶性,这些现象引起了人们对卟啉类化合物液晶性能研究的极大兴趣[3],我们在前文[4～6]报道了meso-四(对烷氧苯基)卟啉及其金属配合物的合成、表征和液晶性研究,但目前仍无meso-四(间烷氧基苯基)卟啉及其金属配合物的液晶性能的报道.本文合成了meso-四(间烷氧基苯基)卟啉及其铜、钴、锌配合物四个系列40个化合物,其中未见文献报道的新化合物35个;研究了其合成、分离、纯化方法;对于长链烷氧基取代的间位卟啉配体及其金属配合物,我们采用石油醚-无水甲醇混合溶剂重结晶和冰盐浴长时间冷冻的方法,首次得到这四个系列化合物的晶体或固体,在偏光显微镜下有明显的双折射现象.我们采用1HNMR,MS,IR,UV,元素分析等分析测试表征手段确证了这些化合物的结构,研究了这四个系列化合物的结构与1HNMR,IR,UV,MS的波谱关系及判据,报道和解析了间位长链烷氧基取代的四苯基卟啉铜配合物的1H NMR研究结果.     

Synthesis,structure, and reactivity of sp carbon chains with bis(phosphine) pentafluorophenylplatinum endgroups: butadiynediyl (C4) through hexadecaoctaynediyl (C16) bridges,and beyond

The reaction of trans-[(C(6)F(5))(p-tol(3)P)(2)PtCl] (PtCl) and butadiyne (cat. CuI, HNEt(2)) gives trans-[(C(6)F(5))(p-tol(3)P)(2)Pt(Ctbond;C)(2)H] (PtC(4)H, 81 %), which reacts with excess HC(triple bond)CSiEt(3) under Hay coupling conditions (O(2), cat. CuCl/TMEDA, acetone) to yield PtC(6)Si (53 %). A solution of PtC(6)Si in acetone is treated with wet nBu(4)NF to generate PtC(6)H. The addition of ClSiMe(3) (F(-) scavenger) and then excess HC(triple bond)CSiEt(3) under Hay conditions gives PtC(8)Si (39 %). Hay homocouplings of PtC(4)H, PtC(6)H, and PtC(8)H (generated in situ analogously to PtC(6)H) yield PtC(8)Pt, PtC(12)Pt, and PtC(16)Pt (97-92 %). Reactions of PtC(4)H and PtC(6)H with PtCl (cat. CuCl, HNEt(2)) give PtC(4)Pt and PtC(6)Pt (69 %, 34 %). The attempted conversion of PtC(8)H to PtC(10)Si affords mainly PtC(16)Pt, with traces of PtC(20)Pt and PtC(24)Pt. The complexes PtC(x)Pt are exceedingly stable (dec pts 234 to 288 degrees C), and Et(3)P displaces p-tol(3)P to give the corresponding compounds Pt'C(8)Pt' and Pt'C(12)Pt' (94-90 %). The effect of carbon chain lengths upon IR nu(C(triple bond)C) patterns (progressively more bands), UV/Vis spectra (progressively red-shifted and more intense bands with epsilon >600 000 M(-1) cm(-1)), redox properties (progressively more difficult and less reversible oxidations), and NMR values are studied, and analyzed with respect to the polymeric sp carbon allotrope "carbyne". The crystal structure of PtC(12)Pt shows a dramatic, unprecedented degree of chain bending, whereas the chains in PtC(8)Pt, Pt'C(12)Pt', and PtC(16)Pt are nearly linear.     

Spectroelectrochemical studies on mixed-valence states in a cyanide-bridged molecular square, [Ru(II)(2)Fe(II)(2)(mu-CN)(4)(bpy)(8)](PF6)(4).CHCl(3).H(2)O

A cyanide-bridged molecular square of [Ru(II) (2)Fe(II) (2)(mu-CN)(4)(bpy)(8)](PF(6))(4).CHCl(3).H(2)O, abbreviated as [Ru(II) (2)Fe(II) (2)](PF(6))(4), has been synthesised and electrochemically generated mixed-valence states have been studied by spectroelectrochemical methods. The complex cation of [Ru(II) (2)Fe(II) (2)](4+) is nearly a square and is composed of alternate Ru(II) and Fe(II) ions bridged by four cyanide ions. The cyclic voltammogram (CV) of [Ru(II) (2)Fe(II) (2)](PF(6))(4) in acetonitrile showed four quasireversible waves at 0.69, 0.94, 1.42 and 1.70 V (vs. SSCE), which correspond to the four one-electron redox processes of [Ru(II) (2)Fe(II) (2)](4+) right arrow over left arrow [Ru(II) (2)Fe(II)Fe(III)] (5+) right arrow over left arrow [Ru(II) (2)Fe(III) (2)](6+) right arrow over left arrow [Ru(II)Ru(III)Fe(III) (2)](7+) right arrow over left arrow [Ru(III) (2)Fe(III) (2)](8+). Electrochemically generated [Ru(II) (2)Fe(II)Fe(III)](5+) and [Ru(II) (2)Fe(III) (2)](6+) showed new absorption bands at 2350 nm (epsilon =5500 M(-1) cm(-1)) and 1560 nm (epsilon =10 500 M(-1) cm(-1)), respectively, which were assigned to the intramolecular IT (intervalence transfer) bands from Fe(II) to Fe(III) and from Ru(II) to Fe(III) ions, respectively. The electronic interaction matrix elements (H(AB)) and the degrees of electronic delocalisation (alpha(2)) were estimated to be 1090 cm(-1) and 0.065 for the [Ru(II) (2)Fe(II)Fe(III) (2)](5+) state and 1990 cm(-1) and 0.065 for the [Ru(II) (2)Fe(III) (2)](6+) states.     

Synthesis and structure of new carborane-substituted cyclotriphosphazenes

The reactions of [N(3)P(3)Cl(6)] with one, two, or three equivalents of the difunctional 1,2-closo-carborane C(2)B(10)H(10)[CH(2)OH](2) and K(2)CO(3) in acetone have been investigated. These reactions led to the new spiro-closo-carboranylphosphazenes gem-[N(3)P(3)Cl(6-2n)[(OCH(2))(2)C(2)B(10)H(10)](n)] (n=1 (1), 2 (2)) and the first fully carborane-substituted phosphazene gem-[N(3)P(3)[(OCH(2))(2)C(2)B(10)H(10)](3)] (3). A bridged product, non-gem-[N(3)P(3)Cl(4)[(OCH(2))(2)C(2)B(10)H(10)]] (4), was also detected. The reaction of the well-known spiro derivatives [N(3)P(3)Cl(2)(O(2)C(12)H(8))(2)] and [N(3)P(3)Cl(4)(O(2)C(12)H(8))] with the same carborane-diol and K(2)CO(3) in acetone gave the new compounds gem-[N(3)P(3)(O(2)C(12)H(8))(3-n)[(OCH(2))(2)C(2)B(10)H(10)](n)] (n=1 (5) or 2 (6), respectively), without signs of intra- or intermolecularly bridged species. Upon treatment with NEt(3) in acetone, compound 5 was converted into the corresponding nido-carboranylphosphazene. However, the reaction of gem-[N(3)P(3)(O(2)C(12)H(8))(2)[(OCH(2))(2)C(2)B(10)H(10)]] (5) with NEt(3) in ethanol instead of acetone proceeded in a different manner to give the new compound (NHEt(3))(2)[N(3)P(3)(O(2)C(12)H(8))(2)(O)[OCH(2)C(2)B(9)H(10)CH(2)OCH(2)CH(3)]] (7). For compounds with two 2,2'-dioxybiphenyl units, gem-[N(3)P(3)(O(2)C(12)H(8))(2)[(OCH(2))(2)C(2)B(10)H(10)]] (5), (NHEt(3))[N(3)P(3)(O(2)C(12)H(8))(2)[(OCH(2))(2)C(2)B(9)H(10)]] (8), and (NHEt(3))(2)[N(3)P(3)(O(2)C(12)H(8))(2)(O)[OCH(2)C(2)B(9)H(10)CH(2)OCH(2)CH(3)]] (7), a mixture of different stereoisomers may be expected. However, for 5 and 7 only the meso compounds seem to be formed, with the same (R,S)-configuration as in the precursor [N(3)P(3)Cl(2)(O(2)C(12)H(8))(2)]. The reaction of 5 to give 8 seems to proceed with a change of configuration at one phosphorus center, giving a racemic mixture. The crystal structures of the nido-carboranylphosphazenes 7 and 8 have been confirmed by X-ray diffraction methods.     

N,N'-ethylenebis(pyridoxylideneiminato) and N,N'-ethylenebis(pyridoxylaminato): synthesis, characterization, potentiometric, spectroscopic, and DFT studies of their vanadium(IV) and vanadium(V) complexes

The Schiff base N,N'-ethylenebis(pyridoxylideneiminato) (H(2)pyr(2)en, 1) was synthesized by reaction of pyridoxal with ethylenediamine; reduction of H(2)pyr(2)en with NaBH(4) yielded the reduced Schiff base N,N'-ethylenebis(pyridoxylaminato) (H(2)Rpyr(2)en, 2); their crystal structures were determined by X-ray diffraction. The totally protonated forms of 1 and 2 correspond to H(6)L(4+), and all protonation constants were determined by pH-potentiometric and (1)H NMR titrations. Several vanadium(IV) and vanadium(V) complexes of these and other related ligands were prepared and characterized in solution and in the solid state. The X-ray crystal structure of [V(V)O(2)(HRpyr(2)en)] shows the metal in a distorted octahedral geometry, with the ligand coordinated through the N-amine and O-phenolato moieties, with one of the pyridine-N atoms protonated. Crystals of [(V(V)O(2))(2)(pyren)(2)].2 H(2)O were obtained from solutions containing H(2)pyr(2)en and oxovanadium(IV), where Hpyren is the "half" Schiff base of pyridoxal and ethylenediamine. The complexation of V(IV)O(2+) and V(V)O(2) (+) with H(2)pyr(2)en, H(2)Rpyr(2)en and pyridoxamine in aqueous solution were studied by pH-potentiometry, UV/Vis absorption spectrophotometry, as well as by EPR spectroscopy for the V(IV)O systems and (1)H and (51)V NMR spectroscopy for the V(V)O(2) systems. Very significant differences in the metal-binding abilities of the ligands were found. Both 1 and 2 act as tetradentate ligands. H(2)Rpyr(2)en is stable to hydrolysis and several isomers form in solution, namely cis-trans type complexes with V(IV)O, and alpha-cis- and beta-cis-type complexes with V(V)O(2). The pyridinium-N atoms of the pyridoxal rings do not take part in the coordination but are involved in acid-base reactions that affect the number, type, and relative amount of the isomers of the V(IV)O-H(2)Rpyr(2)en and V(V)O(2)-H(2)Rpyr(2)en complexes present in solution. DFT calculations were carried out and support the formation and identification of the isomers detected by EPR or NMR spectroscopy, and the strong equatorial and axial binding of the O-phenolato in V(IV)O and V(V)O(2) complexes. Moreover, the DFT calculations done for the [V(IV)O(H(2)Rpyr(2)en)] system indicate that for almost all complexes the presence of a sixth equatorial or axial H(2)O ligand leads to much more stable compounds.     

Coordination algorithms control molecular architecture: [CuI4(L2)4]4+ grid complex versus [MII2(L2)2X4]y+ side-by-side complexes (M=Mn,Co, Ni,Zn; X=solvent or anion) and [FeII(L2)3][Cl3FeIIIOFeIIICl3

The synthesis and characterisation of a pyridazine-containing two-armed grid ligand L2 (prepared from one equivalent of 3,6-diformylpyridazine and two equivalents of p-anisidine) and the resulting transition metal (Zn, Cu, Ni, Co, Fe, Mn) complexes (1-9) are reported. Single-crystal X-ray structure determinations revealed that the copper(I) complex had self-assembled as a [2 x 2] grid, [Cu(I) (4)(L2)(4)][PF(6)](4).(CH(3)CN)(H(2)O)(CH(3)CH(2)OCH(2)CH(3))(0.25) (2.(CH(3)CN)(H(2)O)(CH(3)CH(2)OCH(2)CH(3))(0.25)), whereas the [Zn(2)(L2)(2)(CH(3)CN)(2)(H(2)O)(2)][ClO(4)](4).CH(3)CN (1.CH(3)CN), [Ni(II) (2)(L2)(2)(CH(3)CN)(4)][BF(4)](4).(CH(3)CH(2)OCH(2)CH(3))(0.25) (5 a.(CH(3)CH(2)OCH(2)CH(3))(0.25)) and [Co(II) (2)(L2)(2)(H(2)O)(2)(CH(3)CN)(2)][ClO(4)](4).(H(2)O)(CH(3)CN)(0.5) (6 a.(H(2)O)(CH(3)CN)(0.5)) complexes adopt a side-by-side architecture; iron(II) forms a monometallic cation binding three L2 ligands, [Fe(II)(L2)(3)][Fe(III)Cl(3)OCl(3)Fe(III)].CH(3)CN (7.CH(3)CN). A more soluble salt of the cation of 7, the diamagnetic complex [Fe(II)(L2)(3)][BF(4)](2).2 H(2)O (8), was prepared, as well as two derivatives of 2, [Cu(I) (2)(L2)(2)(NCS)(2)].H(2)O (3) and [Cu(I) (2)(L2)(NCS)(2)] (4). The manganese complex, [Mn(II) (2)(L2)(2)Cl(4)].3 H(2)O (9), was not structurally characterised, but is proposed to adopt a side-by-side architecture. Variable temperature magnetic susceptibility studies yielded small negative J values for the side-by-side complexes: J=-21.6 cm(-1) and g=2.17 for S=1 dinickel(II) complex [Ni(II) (2)(L2)(2)(H(2)O)(4)][BF(4)](4) (5 b) (fraction monomer 0.02); J=-7.6 cm(-1) and g=2.44 for S= 3/2 dicobalt(II) complex [Co(II) (2)(L2)(2)(H(2)O)(4)][ClO(4)](4) (6 b) (fraction monomer 0.02); J=-3.2 cm(-1) and g=1.95 for S= 5/2 dimanganese(II) complex 9 (fraction monomer 0.02). The double salt, mixed valent iron complex 7.H(2)O gave J=-75 cm(-1) and g=1.81 for the S= 5/2 diiron(III) anion (fraction monomer=0.025). These parameters are lower than normal for Fe(III)OFe(III) species because of fitting of superimposed monomer and dimer susceptibilities arising from trace impurities. The iron(II) centre in 7.H(2)O is low spin and hence diamagnetic, a fact confirmed by the preparation and characterisation of the simple diamagnetic iron(II) complex 8. M?ssbauer measurements at 77 K confirmed that there are two iron sites in 7.H(2)O, a low-spin iron(II) site and a high-spin diiron(III) site. A full electrochemical investigation was undertaken for complexes 1, 2, 5 b, 6 b and 8 and this showed that multiple redox processes are a feature of all of them.     

1-Cyclohepta-2,4,6-trienyl-selanes--a 77Se NMR study: indirect nuclear 77Se--13C spin-spin coupling constants and application of density functional theory (DFT) calculations

1-Cyclohepta-2,4,6-trienyl-selanes Se(C(7)H(7))(2) (2c), R--Se--C(7)H(7) with R = Bu, (t)Bu, Ph, 4-F--C(6)H(4) (12a,b,c,d) were prepared by the reaction of the corresponding silanes, Si(SeMe(3))(2) and R--Se--SiMe(3), respectively, with tropylium bromide C(7)H(7)Br. In spite of the low stability of the selanes even in dilute solutions and at low temperature, they could be characterised by their (1)H, (13)C and (77)Se NMR parameters. Coupling constants (1)J((77)Se,(13)C) were measured and calculated by DFT methods at the B3LYP/6-311+G(d,p) level of theory. The comparison of experimental and calculated coupling constants (1)J((77)Se,(13)C) included numerous selenium carbon compounds with largely different Se--C bonds, revealing a satisfactory agreement. Both the spin-dipole (SD) and the paramagnetic spin-orbital (PSO) terms contributed significantly to the spin-spin coupling interaction, in addition to the Fermi contact (FC) term.     

Strong intramolecular secondary si.N bonds in trifluorosilylhydrazines

The simple silylhydrazines F(3)SiN(Me)NMe(2) (1), F(2)Si(N(Me)NMe(2))(2) (2), and F(3)SiN(SiMe(3))NMe(2) (3) have been prepared by reaction of SiF(4) with LiN(Me)NMe(2) and LiN(SiMe(3))NMe(2), while F(3)SiN(SnMe(3))NMe(2) (4) was prepared from SiF(4) and (Me(3)Sn)(2)NNMe(2) (5). The compounds were characterized by gas-phase IR and multinuclear NMR spectroscopy ((1)H, (13)C, (14/15)N, (19)F, (29)Si, (119)Sn), as well as by mass spectrometry. The crystal structures of compounds 1-5 were determined by X-ray crystallography. The structures of free molecules 1 and 3 were determined by gas-phase electron diffraction. The structures of 1, 2, and 4 were also determined by ab initio calculations at the MP2/6-311+G** level of theory. These structural studies constitute the first experimental proof for the presence of strong Si.N beta-donor-acceptor bonds between the SiF(3) and geminal NMe(2) groups in silylhydrazines. The strength of these non-classical Si.N interactions is strongly dependent on the nature of the substituent at the alpha-nitrogen atom of the SiNN unit, and has the order 3>4>1. The valence angles at these extremely deformed alpha-nitrogen atoms, and the Si.N distances are (crystal/gas): 1 104.2(1)/106.5(4) degrees, 2.438(1)/2.510(6) A; 3 83.6(1)/84.9(4) degrees, 2.102(1)/2.135(9) A; 4 89.6(1) degrees, 2.204(2) A.     

Solubilizing sodium fluoride in acetonitrile: synthesis, molecular structure, and complexation behavior of bis(organostannyl)methyl-substituted crown ethers

The synthesis of the crown-ether-substituted bis(organostannyl)methanes Ph(3)SnCH(2)Sn(Ph(2))-CH(2)-[16]crown-5 (1) and Ph(2)ISnCH(2)Sn(I)(Ph)-CH(2)-[16]crown-5 (2) is reported. Both compounds have been characterized by elemental analyses, (1)H, (13)C, (19)F, and (119)Sn NMR spectroscopy, and in the case of compound 2 also by electrospray ionization mass spectrometry. Single-crystal X-ray diffraction analysis revealed for the aqua complex 2.H(2)O trigonal-bipyramidal-configured tin atoms with intramolecular Sn(1)-O(1) and Sn(2)-O(1W) distances of 2.555(2) and 2.440(3) A, respectively. The water molecule is trapped in a sandwich-like fashion between the crown ether oxygen atoms O(2) and O(4) and the Sn(2) atom. NMR spectroscopy unambiguously proved the ability of compound 2 in acetonitrile to overcome the high lattice energy of sodium fluoride and to complex the latter under charge separation.     

A quantum chemistry study: a new kind of boron nitrides

At the B3LYP/6-311+G** and the BP86/6-311+G** levels of theory, BNN, H(3)BNN, NNBH(2)-BH(2)NN, (BNN)(2)H(2), NNBBNN, (BNN)(3) (+), (BNN)(4), (BNN)(4) (2+), (BNN)(4) (2-), B(4)(NN)(2), (BNN)(5) (-), (BNN)(6), (BNN)(7) (+), and (BNN)(8) (2+) are investigated. Neutral (BNN)(4) is aromatic with its triplet state but antiaromatic with its singlet state. (BNN)(4) dication favors D(2d) structure, while (BNN)(4) dianion favors a planar D(4h) structure. (BNN)(3) (+), (BNN)(4) (2-), (BNN)(5) (-), (BNN)(6), (BNN)(7) (+), (BNN)(7) (3-), (BNN)(8) (2+), and (BNN)(8) (2-) are all aromatic with planar monocyclic conformation, following the 4n + 2 rule. Moreover, according to the CASSCF and MRCI calculations, the planar B(4)(NN)(2) of D(2h) symmetry prefers to be a sigma-pi diradical in spite of open-shell singlet or triplet and is also aromatic. Akin to the sigma-pi back interaction in compounds containing transition metal, there exists the sigma-pi back interaction between boron and N(2) ligand among some species reported herein, which strengthens B(-)N bond but activates N-N bond, especially in (4)Sigma(-) BNN. The T-shaped structure lies lowest in energy among seven isomers of the (BNN)(2)H(2) dimer, and the parallel-displaced structure is favored between two isomers of the (BNN)(6) dimer.     

Characterisation of uniformly 13C, 15N labelled bacteriochlorophyll a and bacteriopheophytin a in solution and in solid state: complete assignment of the 13C, 1H and 15N chemical shifts

In this investigation we report a complete assignment of (13)C, (1)H and (15)N solution and solid state chemical shifts of two bacterial photosynthetic pigments, bacteriochlorophyll (BChl) a and bacteriopheophytin (BPheo) a. Uniform stable-isotope labelling strategies were developed and applied to biosynthetic preparation of photosynthetic pigments, namely uniformly (13)C, (15)N labelled BChl a and BPheo a. Uniform stable-isotope labelling with (13)C, (15)N allowed performing the assignment of the (13)C, (15)N and (1)H resonances. The photosynthetic pigments were isolated from the biomass of photosynthetic bacteria Rhodopseudomonas palustris 17001 grown in uniformly (13)C (99%) and (15)N (98%) enriched medium. Both pigments were characterised by NMR in solution (acetone-d(6)) and by MAS NMR in solid state and their NMR resonances were recorded and assigned through standard liquid 2D (13)C-(13)C COSY, (1)H-(13)C HMQC, (1)H-(15)N HMBC and solid 2D (13)C-(13)C RFDR, (1)H-(13)C FSLG HETCOR and (1)H-(15)N HETCOR correlation techniques at 600 MHz and 750 MHz. The characterisation of pigments is of interest from biochemical to pharmaceutical industries, photosynthesis and food research.