聚苯并咪唑金属复合物的X-射线光电子能谱(XPS)研究

本文报道以聚苯并咪唑(PBI)与某些过渡金属卤化物所形成的金属复合物的XPS研究,由反映在金属复合物N_(1s)和C_(1s)振起(Shake-up)伴峰的消失,反映在PBI中N_(1s)双峰变为复合物中的具有高结合能的单峰以及与其复合金属离子结合能的降低,这就从施受两个侧面确证金属复合物的形成。XPS结果也说明在金属复合物的制备中,不同溶剂条件所制得的复合物在硅氢加成中活性丧失归结於溶剂导致的金属离子的还原。     

Tuning the reactivity of dioxoruthenium(VI) porphyrins toward an arylimine by altering porphyrin substituents

Reaction of dioxoruthenium(VI) porphyrins [Ru(VI)(Por)O2] with arylimine HN=CPh2 in dichloromethane afforded bis(methyleneamido)ruthenium(IV) porphyrins [Ru(IV)(Por)(N=CPh2)2] for Por = 4-Cl-TPP and TMP; (methyleneamido)hydroxoruthenium(IV) porphyrins [Ru(IV)(Por)(N=CPh2)(OH)] for Por = TPP and TTP; and bis(arylimine)ruthenium(II) porphyrins [Ru(II)(Por)(HN=CPh2)2] for Por = 3,5-Cl2TPP and 3,5-(CF3)2TPP. In dichloromethane solution exposed to air, complex [Ru(II)(3,5-Cl2TPP)(HN=CPh2)2] underwent oxidative deprotonation to form [Ru(IV)(3,5-Cl2TPP)(N=CPh2)2]. The new ruthenium porphyrins were identified by 1H NMR, UV-vis, IR, and mass spectroscopy, along with elemental analysis. X-ray crystal structure determinations of [Ru(IV)(4-Cl-TPP)(N=CPh2)2], [Ru(IV)(TPP)(N=CPh2)(OH)], and [Ru(II)(3,5-(CF3)2TPP)(HN=CPh2)2] revealed the Ru-N(methyleneamido) or Ru-N(arylimine) distances of 1.897(5) A (average), 1.808(4) A, and 2.044(2) A (average), respectively.     

Reactions of nitrogen oxides with heme models. Characterization of NO and NO2 dissociation from Fe(TPP)(NO2)(NO) by flash photolysis and rapid dilution techniques: Fe(TPP)(NO2) as an unstable intermediate

Described are studies directed toward elucidating the controversial chemistry relating to the solution phase reactions of nitric oxide with the iron(II) porphyrin complex Fe(TPP)(NO) (1, TPP = meso-tetraphenylporphinato2-). The only reaction observable with clean NO is the formation of the diamagnetic dinitrosyl species Fe(TPP)(NO)2 (2), and this is seen only at low temperatures (K(1) < 3 M(-1) at ambient temperature). However, 1 does readily react reversibly with N2O3 in the presence of excess NO to give the nitro nitrosyl complex Fe(TPP)(NO2)(NO) (3), suggesting that previous claims that 1 promotes NO disproportionation to give 3 may have been compromised by traces of air in the nitric oxide sources. It is also noted that 3 undergoes reversible loss of NO to give the elusive nitro species Fe(TPP)(NO2) (4), which has been implicated as a powerful oxygen atom transfer agent in reactions with various substrates. Furthermore, in the presence of excess NO2, the latter undergoes oxidation to the stable nitrato analogue Fe(TPP)(NO3) (5). Owing to such reactivity of Fe(TPP)(NO2), flash photolysis and stopped-flow kinetics rather than static techniques were necessary for the accurate measurement of dissociation equilibria characteristic of Fe(TPP)(NO2)(NO) in 298 K toluene solution. Flash photolysis of 3 resulted in competitive NO2 and NO dissociation to give Fe(TPP)(NO) and Fe(TPP)(NO2), respectively. The rate constant for the reaction of 1 with N2O3 to generate Fe(TPP)(NO2)(NO) was determined to be 1.8 x 10(6) M(-1) s(-1), and that for the NO reaction with 4 was similarly determined to be 4.2 x 10(5) M(-1) s(-1). Stopped-flow rapid dilution techniques were used to determine the rate constant for NO dissociation from 3 as 2.6 s(-1). The rapid dilution experiments also demonstrated that Fe(TPP)(NO2) readily undergoes further oxidation to give Fe(TPP)(NO3). The mechanistic implications of these observations are discussed, and it is suggested that NO2 liberated spontaneously from Fe(P)(NO2) may play a role in an important oxidative process involving this elusive species.     

A rare mu-hydroxo-bridged species. synthesis, structure, and properties of mu-hydroxo(tetraphenylporphyrinatomanganese(III))(phthalocyaninato(azido)chromium(III)), [(TPP)Mn-O(H)-CrPc(N3)

A novel ditetrapyrrolic, heteroleptic, and heterometallic (Mn-Cr) mu-hydroxo-bridged complex has been prepared, and its structural and general properties have been studied. The species mu-hydroxo(tetraphenylporphyrinatomanganese(III))(phthalocyaninato(azido)chromium(III)), [(TPP)Mn-O(H)-CrPc(N3)], isolated as a chloronaphthalene (ClNP) solvate, has been structurally characterized by single-crystal X-ray work. The two (TPP)Mn and CrPc(N3) fragments are held together by the bridging mu-hydroxo ion with long Mn-O [1.993(5) A] and Cr-O [1.976(5) A] bond distances and a Mn-O(H)-Cr angle of 163.7(3) degrees . The five-coordinate Mn center in the (TPP)Mn fragment is displaced from the TPP rigorously planar central N4 core by 0.128 A, and the environment is typical of a Mn(III) high-spin site. The six-coordinate Cr(III) in the CrPc(N3) moiety lies practically in the plane of the phthalocyanine macrocycle (displacement toward the azido group: 0.054 A). The average Mn-N(pyr) and Cr-N(pyr) bond distances are 2.011(6) and 1.982(6) A, respectively, and the Mn-Cr bond distance is 3.929(2) A. The porphyrin and phthalocyanine rings are in an almost eclipsed position [5.16(2) degrees ], and the mean planes of the two macrocycles form a dihedral angle of 5.79(4) degrees. Crystal data for [(TPP)Mn-O(H)-CrPc(N3)].2ClNP, C76H45CrMnN15O.2C10H7Cl: a = 16.645(3) A, b = 17.692(4) A, c = 25.828(5) A, alpha = 90 degrees , beta = 98.79(3) degrees , gamma = 90 degrees , space group P2(1)/c (No. 14), V = 7517(3) A(3), Z = 4, R1 = 0.086, and wR2 = 0.267. IR and UV-vis-near-IR spectral and room temperature magnetic susceptibility data of the [Mn-Cr] species are also presented.     

Spectroscopic properties and electronic structure of five- and six-coordinate iron(II) porphyrin NO complexes: Effect of the axial N-donor ligand

In this paper, the differences in the spectroscopic properties and electronic structures of five- and six-coordinate iron(II) porphyrin NO complexes are explored using [Fe(TPP)(NO)] (1; TPP = tetraphenylporphyrin) and [Fe(TPP)(MI)(NO)] (2; MI = 1-methylimidazole) type systems. Binding of N-donor ligands in axial position trans to NO to five-coordinate complexes of type 1 is investigated using UV-vis absorption and 1H NMR spectroscopies. This way, the corresponding binding constants Keq are determined and the 1H NMR spectra of 1 and 2 are assigned for the first time. In addition, 1H NMR allows for the determination of the degree of denitrosylation in solutions of 1 with excess base. The influence of the axial ligand on the properties of the coordinated NO is then investigated. Vibrational spectra (IR and Raman) of 1 and 2 are presented and assigned using isotope substitution and normal-coordinate analysis. Obtained force constants are 12.53 (N-O) and 2.98 mdyn/A (Fe-NO) for 1 compared to 11.55 (N-O) and 2.55 mdyn/A (Fe-NO) for 2. Together with the NMR results, this provides experimental evidence that binding of the trans ligand weakens the Fe-NO bond. The principal bonding schemes of 1 and 2 are very similar. In both cases, the Fe-N-O subunit is strongly bent. Donation from the singly occupied pi* orbital of NO into d(z2) of iron(II) leads to the formation of an Fe-NO sigma bond. In addition, a medium-strong pi back-bond is present in these complexes. The most important difference in the electronic structures of 1 and 2 occurs for the Fe-NO sigma bond, which is distinctively stronger for 1 in agreement with the experimental force constants. The increased sigma donation from NO in 1 also leads to a significant transfer of spin density from NO to iron, as has been shown by magnetic circular dichroism (MCD) spectroscopy in a preceding Communication (Praneeth, V. K. K.; Neese, F.; Lehnert, N. Inorg. Chem. 2005, 44, 2570-2572). This is confirmed by the 1H NMR results presented here. Hence, further experimental and computational evidence is provided that complex 1 has noticeable Fe(I)NO+ character relative to 2, which is an Fe(II)NO(radical) complex. Finally, using MCD theory and quantum chemical calculations, the absorption and MCD C-term spectra of 1 and 2 are assigned for the first time.     

Synthesis,characterization, and laser flash photolysis reactivity of a carbonmonoxy heme complex

We present here the synthesis, characterization, and flash photolysis study of [(F(8)TPP)Fe(II)(CO)(THF)] (1) [F(8)TPP = tetrakis(2,6-difluorophenyl)porphyrinate(2-)]. Complex 1 crystallizes from THF/heptane solvent system as a tris-THF solvate, [(F(8)TPP)Fe(II)(CO)(THF)].3THF (1.3THF), with ferrous ion in the porphyrin plane (C(61)H(52)F(8)FeN(4)O(5); a = 11.7908(2) A, b = 20.4453(2) A, c = 39.9423(3), alpha = 90 degrees, beta = 90 degrees, gamma = 90 degrees; orthorhombic, P2(1)2(1)2(1), Z = 8; Fe-N(4)(av) = 2.00 A; N-Fe-N (all) = 90.0 degrees ). This complex (as 1.THF) has also been characterized by (1)H NMR [six-coordinate, low-spin heme; CD(3)CN, RT, delta 8.82 (s, pyrrole-H, 8H), 7.89 (s, para-phenyl-H, 8H), 7.46 (s, meta-phenyl-H, 4H), 3.58 (s, THF, 8H), 1.73 (s, THF, 8H)], (2)H NMR (pyrrole-deuterated analogue) [(F(8)TPP-d(8))Fe(II)(CO)(THF)] [THF, RT, delta 8.78 ppm (s, pyrrole-D)], (13)C NMR (on (13)CO-enriched adduct) [THF-d(8), RT, delta 206.5 ppm; CD(2)Cl(2), RT, delta 206.1 ppm], UV-vis [THF, RT, lambda(max), 411 (Soret), 525 nm], and IR [293 K, solution, nu(CO) 1979 cm(-)(1) (THF), 1976 cm(-)(1) (acetone), 1982 cm(-)(1) (CH(3)CN)] spectroscopies. In order to more fully understand the intricacies of solvent-ligand binding (as compared to CO rebinding to the photolyzed heme), we have also synthesized the bis-THF adduct [(F(8)TPP)Fe(II)(THF)(2)]. Complex 2 also crystallizes from THF/heptane solvent system as a bis-THF solvate, [(F(8)TPP)Fe(II)(THF)(2)].2THF (2.2THF), with ferrous iron in the porphyrin plane (C(60)H(52)F(8)FeN(4)O(4); a = 21.3216(3) A, b = 12.1191(2) A, c = 21.0125(2) A, alpha = 90 degrees, beta = 105.3658(5) degrees, gamma = 90 degrees; monoclinic, C2/c, Z = 4; Fe-N(4)(av) = 2.07 A; N-Fe-N (all) = 90.0 degrees ). Further characterization of 2 includes UV-vis [THF, lambda(max), 421 (Soret), 542 nm] and (1)H NMR [six-coordinate, high spin heme; THF-d(8), RT, delta 56.7 (s, pyrrole-H, 8H), 8.38 (s, para-phenyl-H, 8H), 7.15 (s, meta-phenyl-H, 4H)] spectroscopies. Flash photolysis studies employing 1 were able to resolve the CO rebinding kinetics in both THF and cyclohexane solvents. In CO saturated THF [[CO] approximately 5 mM] and at [1] congruent with 5 microM, the conversion of [(F(8)TPP)Fe(II)(THF)(2)] (produced after photolytic displacement of CO) to [(F(8)TPP)Fe(II)(CO)(THF)] was monoexponential, with k(obs) = 1.6 (+/-0.2) x 10(4) s(-)(1). Reduction in [CO] by vigorous Ar purging gave k(obs) congruent with 10(3) s(-)(1) in cyclohexane. The study presented in this report lays the foundation for applying fast-time scale studies based on CO flash photolysis to the more complicated heterobimetallic heme/Cu systems.     

四苯基卟啉对二苯并咪唑光电导性能的敏化

采用溶剂球磨分散法制备了四苯基卟啉(H₂TPP)/二苯并咪唑(Im-PTC)复合光生材料,用浸涂法将其制成功能分离型双层光导体.采用光致释电法对其光电导性能进行测试,发现在500nm下,由质量分数5%H₂TPP/40%Im-PTC复合光生材料制备的光导体的光敏性比单纯40%的Im-PTC制备的光导体提高了3.5倍,说明H₂TPP对Im-PTC有明显的敏化作用.进一步研究了该复合材料的电子结构,结果表明,H₂TPP与Im-PTC存在分子间的光致电荷转移,从而提高了电荷的光生和分离效率,增强了光导体的光敏性.     

Attenuation lengths in organic materials

Measurements are reported for attenuation lengths in overlayers of guanine, poly(styrene), poly(methyl methacrylate) and poly(2‐vinylpyridine) in the energy range 700–1400 eV to evaluate the accuracy of theoretical computations and generic equations. The layers are deposited on gold, either by evaporation and condensation or by spin casting. Measurements are made by X‐ray photoelectron spectroscopy (XPS) for the substrate Au 4f, 4d and 4p peaks as well as the overlayer N 1s peak in guanine and poly(2‐vinylpyridine). These measurements all correlate with the theory of Tanuma, Powell and Penn, to an RMS deviation of 11%. Correlations with the predictions using the generic equation known as TPP‐2M exhibit a poorer RMS deviation of 20%. Use of an ‘average’ organic material for the inelastic mean free paths for the four materials also leads to a 20% RMS deviation. Additional data are also presented for Irganox 1010 that is used, increasingly, as a reference sample for secondary ion mass spectrometry. Comparisons for 5 materials with the Gries G1 formula gives an RMS deviation of 13%, but a small change to interpolate between Gries' classes of organic materials with H/C being around either 1 or 2, leads to a reduced RMS deviation of 10%. This final version, G1‐SS, requiring only the material density and chemical formula, is very simple to use for all organic materials where these data are known or can be estimated. © Crown copyright 2010. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.     

Photophysical properties of a rhodium tetraphenylporphyrin-tin corrole dyad. The first example of a through metal-metal bond energy transfer

The luminescence spectroscopy study and the determination of the photophysical parameters for the M-M'-bonded rhodium meso-tetraphenylporphyrin-tin(2,3,7,13,17,18-hexamethyl-8,12-diethylcorrole) complex, (TPP)Rh-Sn(Me6Et2Cor) 1, was investigated. The emission bands as well as the lifetimes (tau(e)) and the quantum yields (Phi(e); at 77 K using 2MeTHF as solvent) were compared with those of (TPP)RhI 2 (TPP = tetraphenylporphyrin) and (Me6Et2Cor)SnCl 3 (Me6Et2Cor = 2,3,7,13,17,18-hexamethyl-8,12-diethylcorrole) which are the two chemical precursors of 1. The energy diagram has been established from the absorption, fluorescence and phosphorescence spectra. The Rh(TPP) and Sn(Me6Et2Cor) chromophores are the energy donor (D) and acceptor (A), respectively. The total absence of fluorescence in 1 (while fluorescence is observed in the tin derivative 3) indicates efficient excited state deactivation, presumably due to heavy atom effect and intramolecular energy transfer (ET). The large decreases in tau(P) and Phi(P) of the Rh(TPP) chromophore going from 2 to 1 indicate a significant intramolecular ET in the triplet states of 1 with an estimated rate ranging between 10(6) and 10(8) s(-1). Based on the comparison of transfer rates with other related dyads that exhibit similar D-A separations and no M-M' bond, and for which slower through space ET processes (10(2)-10(3) s(-1)) operate, a through M-M' bond ET has been unambiguously assigned to 1.     

Hydrogen atom transfer reactions of iron-porphyrin-imidazole complexes as models for histidine-ligated heme reactivity

Hydrogen atom transfer (HAT) reactions of the bis(histidine) cytochrome active site models (TPP)FeII(ImH)2 (FeIIImH) and (TPP)Fe(Im)(ImH) (FeIIIIm) have been examined in acetonitrile solvent (TPP = tetraphenylporphyrin, ImH = 4-methylimidazole). The ascorbate derivative 5,6-isopropylidine ascorbate, hydroquinone, and the hydroxylamine TEMPOH all rapidly add H* to FeIIIIm to give FeIIImH. Similarly, the phenoxyl radical 2,4,6-tBu3C6H2O* and excess TEMPO* each oxidize FeIIImH to give FeIIIIm. On the basis of redox potential, pKa, and equilibrium measurements, the N-H bond in FeIIImH was found to have a bond dissociation free energy (BDFE) of 70 +/- 2 kcal mol(-1). A hydrogen atom transfer mechanism (concerted transfer of e- and H+) is indicated based on data for the ascorbate and TEMPO* reactions.     

氧化碘苯间氨基苯甲酸锰(IV)四苯基卟啉配合物的合成

高价锰卟啉配合物在温和条件下分解水,释放氧,是植物光体体II的可能模型化合物.我们选择间氨基苯甲酸作为轴向配体,在二氯甲烷中用氧化碘苯氧化H2NC6H4COOMn(III)TPP相似文献   

Molecular mechanism of thiamine pyrophosphate import into mitochondria: a molecular simulation study

The import of thiamine pyrophosphate (TPP) through both mitochondrial membranes was studied using a total of 3-µs molecular dynamics simulations. Regarding the translocation through the mitochondrial outer membrane, our simulations support the conjecture that TPP uses the voltage-dependent anion channel, the major pore of this membrane, for its passage to the intermembrane space, as its transport presents significant analogies with that used by other metabolites previously studied, in particular with ATP. As far as passing through the mitochondrial inner membrane is concerned, our simulations show that the specific carrier of TPP has a single binding site that becomes accessible, through an alternating access mechanism. The preference of this transporter for TPP can be rationalized mainly by three residues located in the binding site that differ from those identified in the ATP/ADP carrier, the most studied member of the mitochondrial carrier family. The simulated transport mechanism of TPP highlights the essential role, at the energetic level, of the contributions coming from the formation and breakage of two networks of salt bridges, one on the side of the matrix and the other on the side of the intermembrane space, as well as the interactions, mainly of an ionic nature, formed by TPP upon its binding. The energy contribution provided by the cytosolic network establishes a lower barrier than that of the matrix network, which can be explained by the lower interaction energy of TPP on the matrix side or possibly a uniport activity.

     

Antiviral potential of natural compounds against influenza virus hemagglutinin

Influenza virus of different subtypes H1N1, H2N2, H3N2 and H5N1 cause many human pandemic deaths and threatening the people worldwide. The Hemagglutinin (HA) protein mediates viral attachment to host receptors act as an attractive target. The sixteen natural compounds have been chosen to target the HA protein. Molecular docking studies have been performed to find binding affinity of the compounds. Out of the sixteen, three compounds CI, CII and CIII found to posses a higher binding affinity. The molecular dynamics (MD) simulation has been performed to study the structural, dynamical properties for the nine different complexes CI, CII, CIII bound with H1, H2, H3 proteins and the results were compared. The molecular mechanics Poission-Boltzmann surface area (MM-PBSA) method is used to compare the binding free energy, its different energy components and per residue binding contribution. The H1 subtype shows higher binding preference for all the curcumin derivatives than H2 and H3. The binding capability of protein subtypes with curcumin derivatives and the binding affinity of curcumin compounds are in the order H1 > H2 > H3 and CI > CII > CIII respectively. The two -O-CH3- groups present in the CI compound help to have strong binding with HA protein than CII and CIII. The van der Waals interaction energy plays a significant role for binding in all the complexes. The hydrogen bonding interactions were monitored throughout the MD simulation. The conserved region (153–155) and the helix region (193–194) of H1, H2, H3 protein subtypes are found to possess higher binding susceptibility for binding of the curcumin derivatives.     

酞菁（H_2TAP）的X－射线光电子能谱（XPS）

酞菁（Ｈ_２ＴＡＰ）的Ｘ－射线光电子能谱（ＸＰＳ）朱志昂，卜显和，刘月霞（南开大学化学系天津３０００７１）ＰａｕｌＧ．Ｇａｓｓｍａｎ（美国明尼苏达大学化学系）关键词酞青，ＸＰＳ，Ｃ１ｓ电子结合能，Ｎ１ｓ电子结合能酞菁及其金属配合物作为叶绿素，血红素的?..     

Reactions of nitrogen oxides with heme models. Spectral and kinetic study of nitric oxide reactions with solid and solute Fe(III)(TPP)(NO3)

The reaction(s) of nitric oxide (nitrogen monoxide) gas with sublimed layers containing the nitrato iron(III) complex Fe(III)(TPP)(eta(2)-O(2)NO) (1, TPP = meso-tetraphenyl porphyrinate(2)(-)) leads to formation of several iron porphyrin species that are ligated by various nitrogen oxides. The eventual products of these low-temperature solid-state reactions are the nitrosyl complex Fe(TPP)(NO), the nitro-nitrosyl complex Fe(TPP)(NO(2))(NO), and 1 itself, and the relative final quantities of these were functions of the NO partial pressure. It is particularly notable that isotope labeling experiments show that the nitrato product is not simply unreacted 1 but is the result of a series of transformations taking place in the layered material. Thus, the nitrato complex formed from solid Fe(TPP)(eta(2)-O(2)NO) maintained under a (15)NO atmosphere was found to be the labeled analogue Fe(TPP)(eta(2)-O(2)(15)NO). The reactivities of the layered solids are compared to the behaviors of the same species in ambient temperature solutions. To interpret the reactions of the labeled nitrogen oxides, the potential exchange reactions between N(2)O(3) and (15)NO were examined, and complete isotope scrambling was observed between these species under the reaction conditions (T = 140 K). Overall it was concluded from isotope labeling experiments that the sequence of reactions is initiated by reaction of 1 with NO to give the nitrato nitrosyl complex Fe(TPP)(eta(1)-ONO(2))(NO) (2) as an intermediate. This is followed by a reaction in the presence of excess NO that is equivalent to the loss of the nitrate radical NO(3)(*)( )()to give Fe(TPP)(NO) as another transient species. A plausible pathway involving NO attack on the coordinated nitrate of 2 resulting in the release of N(2)O(4) concerted with electron transfer to the metal center is proposed.     

Enhanced conductivity of thin film polyaniline by self-assembled transition metal complexes

In a recent study, the transition metal complex, cis-dichlorobis(2-,2'-dipyridyl)ruthenium (II) (Ru(bpy)2Cl2), and the macrocycle Ru(TPP)CO (TPP:- tetraphenylporphine) were bound to pyridine terminated self-assembled monolayers on quartz. Following modification of the quartz surface with metal complexes, the conducting polymer polyaniline was deposited via in situ polymerization. The sheet conductivity (as measured by the four-probe method) of the resulting polyaniline films deposited onto Ru(bpy)2Cl2 and Ru(TPP)CO surfaces was significantly enhanced relative to films deposited onto unmodified quartz. It is postulated that either the macrocycle or the transition metal complex-modified surface interacts with the conducting polymer as it is forming, resulting in a more ordered expanded coil conformation for the polymer. The net result of such an interaction is a thin film possessing significantly greater electrical conductivity.     

Structure and photochemistry of nitrocobalt(III) tetraphenylporphyrin with axial triphenylphosphine in toluene solutions

Thermal and photochemical reactions of nitroaquacobalt(III) tetraphenylporphyrin, (NO(2))(H(2)O)Co(III)TPP, have been investigated in toluene solutions containing triphenylphosphine, P phi(3). It is found that Pphi(3) thermally abstracts an oxygen atom from the NO(2) moiety of (NO(2))(H(2)O)Co(III)TPP with a rate constant 0.52 M(-1) s(-1), resulting in the formation of nitrosylcobalt porphyrin, (NO)CoTPP. The 355-nm laser photolysis of (NO(2))(H(2)O)Co(III)TPP at low concentrations of P phi(3) (<1.0 x 10(-4) M) gives Co(II)TPP and NO(2) as intermediates. The recombination reaction of Co(II)TPP and NO(2) initially forms the coordinately unsaturated nitritocobalt(III) tetraphenylporphyrin, (ON-O)Co(III)TPP, which reacts with P phi(3) to yield nitro(triphenylphosphine)cobalt(III) tetraphenylporphyrin, (NO(2))(P phi(3))Co(III)TPP. Subsequently, the substitution reaction of the axial P phi(3) with H(2)O leads to the regeneration of (NO(2))(H(2)O)Co(III)TPP. From the kinetic studies, the substitution reaction is concluded to occur via a coordinately unsaturated nitrocobalt(III) porphyrin, (NO(2))Co(III)TPP. At higher concentrations of P phi(3) (>4 x 10(-3) M), (NO(2))(H(2)O)Co(III)TPP reacts with P phi(3) to form (NO(2))(P phi(3))Co(III)TPP: the equilibrium constant is obtained as K = 4.3. The X-ray structure analysis of (NO(2))(P phi(3))Co(III)TPP reveals that the P-Co-NO(2) bond angle is 175.0(2) degrees and the bond length Co-NO(2) is 2.000(7) A. In toluene solutions of (NO(2))(H(2)O)Co(III)TPP containing P phi(3) (>4 x 10(-3) M), the major light-absorbing species is (NO(2))(P phi(3))Co(III)TPP, which yields (NO)CoTPP by continuous photolysis. The laser photolysis of (NO(2))(P phi(3))Co(III)TPP gives Co(II)TPP, NO(2), and P phi(3) as initial products. The NO(2) molecule is suggested to be reduced by P phi(3) to yield NO, and the reaction between NO and Co(II)TPP gives (NO)CoTPP. The quantum yield for the photodecomposition of (NO(2))(P phi(3))Co(III)TPP is determined as 0.56.     

Mononuclear copper(I) complexes with triphenylphosphine and N,N′-disubstituted thioureas: synthesis,characterization, and biological evaluation

Abstract

Twelve new complexes, of the general formula CuCl(TPP)₂Tu^1–12 (Tu?=?thiourea), were synthesized by the reaction of CuCl(TPP)₃ (TPP?=?triphenylphosphine) and various N,N′-disubstituted thioureas. The structures of the synthesized complexes were characterized by different techniques such as Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy (¹H, ¹³C, ³¹P, and ¹⁹F), and the representative complexes (1, 2 and 12) were analyzed via single crystal X-ray diffraction. The single crystal X-ray analysis revealed that copper(I) is coordinated with chlorine, two TPP, and the thiourea ligands through the sulfur atom in a mononuclear distorted tetrahedral mode. The compounds were tested for antibacterial, antifungal, cytotoxicity, antileishmanial, and antioxidant activities. The results showed that the synthesized complexes are significantly more active than the free ligands and the commercial reference compounds. The high biological activities of the complexes versus free ligands can be attributed to the copper(I) chloride complexation with thiourea ligands. The synthesized complexes were also evaluated, both experimentally and theoretically, for DNA binding studies. The UV-visible spectroscopic and molecular docking studies demonstrated that the complexes are conjugating with DNA through a groove binding mode.     

Redox properties of ruthenium nitrosyl porphyrin complexes with different axial ligation: structural, spectroelectrochemical (IR, UV-visible, and EPR), and theoretical studies

Experimental and computational results for different ruthenium nitrosyl porphyrin complexes [(Por)Ru(NO)(X)] ( n+ ) (where Por (2-) = tetraphenylporphyrin dianion (TPP (2 (-) )) or octaethylporphyrin dianion (OEP (2-)) and X = H 2O ( n = 1, 2, 3) or pyridine, 4-cyanopyridine, or 4- N,N-dimethylaminopyridine ( n = 1, 0)) are reported with respect to their electron-transfer behavior. The structure of [(TPP)Ru(NO)(H 2O)]BF 4 is established as an {MNO} species with an almost-linear RuNO arrangement at 178.1(3) degrees . The compound [(Por)Ru(NO)(H 2O)]BF 4 undergoes two reversible one-electron oxidation processes. Spectroelectrochemical measurements (IR, UV-vis-NIR, and EPR) indicate that the first oxidation occurs on the porphyrin ring, as evident from the appearance of diagnostic porphyrin radical-anion vibrational bands (1530 cm (-1) for OEP (*-) and 1290 cm (-1) for TPP (*-)), from the small shift of approximately 20 cm (-1) for nu NO and from the EPR signal at g iso approximately 2.00. The second oxidation, which was found to be electrochemically reversible for the OEP compound, shows a 55 cm (-1) shift in nu NO, suggesting a partially metal-centered process. The compounds [(Por)Ru(NO)(X)]BF 4, where X = pyridines, undergo a reversible one-electron reduction. The site of the reduction was determined by spectroelectrochemical studies to be NO-centered with a ca. -300 cm (-1) shift in nu NO. The EPR response of the NO (*) complexes was essentially unaffected by the variation in the substituted pyridines X. DFT calculations support the interpretation of the experimental results because the HOMO of [(TPP)Ru(NO)(X)] (+), where X = H 2O or pyridines, was calculated to be centered at the porphyrin pi system, whereas the LUMO of [(TPP)Ru(NO)(X)] (+) has about 50% pi*(NO) character. This confirms that the (first) oxidation of [(Por)Ru(NO)(H 2O)] (+) occurs on the porphyrin ring wheras the reduction of [(Por)Ru(NO)(X)] (+) is largely NO-centered with the metal remaining in the low-spin ruthenium(II) state throughout. The 4% pyridine contribution to the LUMO of [(TPP)Ru(NO)(py)] (+) is correlated with the stability of the reduced form as opposed to that of the aqua complex.     

Complexation of diphenyl(phenylacetenyl)phosphine to rhodium(III) tetraphenyl porphyrins: synthesis and structural,spectroscopic, and thermodynamic studies

The coordination of diphenyl(phenylacetenyl)phosphine (DPAP, 1) to (X)Rh(III)TPP (X = I (2) or Me (3); TPP = tetraphenyl porphyrin) was studied in solution and in the solid state. The iodide is readily displaced by the phosphine, leading to the bis-phosphine complex [(DPAP)(2)Rh(TPP)](I) (4). The methylide on rhodium in 3 is not displaced, leading selectively to the mono-phosphine complex (DPAP)(Me)Rh(TPP) (5). The first and second association constants, as determined by isothermal titration calorimetry and UV-vis titrations, are in the range 10(4)-10(7) M(-1) (in CH(2)Cl(2)). Using LDI-TOF mass spectrometry, the mono-phosphine complexes can be detected but not the bis-phosphine complexes. The electronic spectrum of 4 is similar to those previously reported with other tertiary phosphine ligands, whereas (DPAP)(I)Rh(TPP) (6) displays a low energy B-band absorption and a high energy Q-band absorption. In contrast to earlier reports, displacement of the methylide on rhodium in 5 could not be observed at any concentration, and the electronic spectra of 4 and 5 are almost identical. Isothermal titration calorimetry experiments showed that all binding events are exothermic, and all are enthalpy driven. The largest values of DeltaG degrees are found for 6. The thermodynamic and UV-vis data reveal that the methylide and the phosphine ligand have an almost identical electronic trans-influence on the sixth ligand.