Generation and dissociation of oxygen‐ and chloride‐bridged iron(III) and manganese(III) tetraphenylporphyrin dimer ions in the gas phase

Electrospray ionization mass spectrometry (ESI/MS) has allowed the discovery of novel dimer ions emerging from solutions of metalloporphyrin salts and their investigation by collision‐induced dissociation (CID) with N₂ molecules. ESI mass spectra have been recorded for the formation of the oxygen or chloride‐bridged dimer ions [(FeTPP)₂OH]⁺, [(MnTPP)₂OH]⁺, [(FeTPP)₂Cl]⁺ and [(MnTPP)₂Cl]⁺ derived from various solutions of FeTPPCl and MnTPPCl salts. The CID of [(FeTPP)₂OH]⁺ proceeds mainly by neutral loss of (FeTPP)OH to form [FeTPP]⁺ and, to a minor extent, to form the charge‐reversed products. The CID of [(MnTPP)₂OH]⁺ exhibits exclusively the product ion [MnTPP]⁺ by loss of neutral (MnTPP)OH. [(FeTPP)₂Cl]⁺ and [(MnTPP)₂Cl]⁺ dissociate by loss of (Fe/MnTPP)Cl to give rise to [Fe/MnTPP]⁺. [(FeTPP)₂O]⁺ and [(FeTPP)₂OH]⁺ were generated from a solution of the dimer, (FeTPP)₂O. Dissociation of [(FeTPP)₂O]⁺ yields two product ions, [FeTPP]⁺ and [(FeTPP)O]⁺, with higher onsets compared to the equivalent fragments formed from [(FeTPP)₂OH]⁺. Copyright © 2009 John Wiley & Sons, Ltd.     

Self-assembly of meso-mono-4-pyridyltriphenylporphyrinatoiron(ii) in sublimed layers. Interaction with molecular oxygen

Low-temperature (T = 80 K) interaction of the sublimed layers of meso-mono-4-pyridyltriphenylporphyrinatoiron(ii) (FeMPyTPP) with dioxygen was studied by IR and electronic absorption spectroscopies. Unlike the meso-tetraphenylporphyrinatoiron(ii) (FeTPP) layers, coordination of O₂ with FeMPyTPP produces extra-complexes of two types: in the first complex one of the axial sites is free, while in the second complex an axial site is occupied by the pyridine group of the adjacent molecule. The results obtained indicate self-assembly of the FeMPyTPP molecules through coordination bonds between the iron atom and pyridine group of the adjacent molecule in the layer. The bonding of O₂ by the sublimed FeMPyTPP layers differs substantially from that by the FeTPP layers, which rapidly loose their ability of oxygen bonding at room temperature.     

Amperometric Biosensor Based on Immobilization Acetylcholinesterase on Manganese Porphyrin Nanoparticles for Detection of Trichlorfon with Flow‐Injection Analysis System

A highly sensitive amperometric biosensor for the detection of organophosphate pesticides (OPs) is developed. The biosensor was fabricated by immobilized acetylcholinesterase (AChE) on manganese (III) meso‐tetraphenylporphyrin (MnTPP) nanoparticles (NPs)‐modified glassy carbon (GC) electrode. The MnTPP NPs used in this article were synthesized by mixing solvent techniques. AChE enzyme was immobilized on the MnTPP NPs surface by conjugated with chitosan (CHIT). The electrocatalytic activity of MnTPP NPs led to a greatly improved performance for thiocholine (TCh) product detection. The developed AChE‐CHIT/MnTPPNP/GC biosensor integrated with a flow‐injection analysis (FIA) system was used to monitor trichlorfon (typical OP). A wide linear inhibition response for trichlorfon is observed in the range of 1.0 nM–1.0 mM, corresponding to 10–83% inhibition for AChE with a detection limit of 0.5 nM.     

Electrochemical Detection of Superoxide Anion Released by Living Cells by Manganese(III) Tetraphenyl Porphine as Superoxide Dismutase Mimic

Superoxide anion, one of the most active reactive oxygen species, is associated with the development of many diseases. So monitoring superoxide anion in living cells is of great significance for the pathological research of many diseases. In this work, a new non-enzymatic sensor for the detection of superoxide anion(O₂^·-) was developed, which was fabricated by the nanocomposites composed of manganese(III) tetraphenyl porphine(MnTPP) as super-oxide dismutase mimic and electrochemical reduced graphene oxide(ERGO) as electrode support material to modify the glassy carbon electrode(GCE). The electrochemical behavior of the fabricated electrode(MnTPP/ERGO/GCE) was performed by electrochemical impedance spectroscopy(EIS) and cyclic voltammetry(CV), which revealed that MnTPP/ERGO/GCE possessed good catalytic ability to the electrochemical reduction of O₂^·-. The MnTPP/ERGO/GCE showed excellent electroanalysis performance towards O₂^·- using the technique of differential pulse voltammetry(DPV) with a linear relationship in the range of 0.2-110.0 μmol/L, a sensitivity of 445 μA·L·mmol^-1·cm^-2 and a detection limit of 0.039 μmol/L(S/N=3). The real-time monitoring of O₂^·- from MCF-7 breast cancer cells stimulated by zymosan was realized in this work, which indicates that the MnTPP/ERGO/GCE hold potential application for electrochemical quantification of superoxide anions in biological applications.     

Oxidation of dyes by manganese tetraphenyl porphyrin activated peroxy bleach

The oxidation of a number of dyes in predominantly aqueous systems by tetraphenylporphyrinato manganese(III) imidazole, MnTPP(Im), activated peroxy bleach has been studied in the context of application in detergent systems. Dyes with an olefinic linkage in the chromophoric group are readily oxidized by perborate even in the absence of the activator. On the other hand, dyes with an azo linkage are resistant to oxidation and are bleached only to a limited extent (25%) even by MnTPP(Im) activated perborate. In the presence of a surfactant, alkylbenzene sulphonate, bleaching is further inhibited by micellar solubilization of the dyes. Sulphonation of MnTPP(Im) only marginally improves the bleaching efficiency in presence of the surfactant. MnTPP(Im) is also destroyed by perborate in the absence of the substrate. In view of these limitations, the metalloporphyrin activated peroxy bleach system is not promising for application in detergent systems. Attempts have also been made to explain the difference in the behaviour of different substrates on structural consideration.     

Evidence for specific solvation of two halocarbene amides

Laser flash photolysis (LFP, 308 nm) of endo-10-halo-10'-N,N-dimethylcarboxamidetricyclo[4.3.1.0]-deca-2,4-diene (1Cl and 1F) releases indan and halocarbene amide (2Cl and 2F). Although the carbenes are not UV-vis active, they react rapidly with pyridine to form ylides (4Cl, 4F), which are readily detected in LFP experiments (lambda(max) = 450 nm). Dioxane decreases the observed rate of carbene reaction with pyridine in CF(2)ClCFCl(2). Small amounts of THF decrease the observed rate of reaction of carbene 2F with pyridine but increase the rate of reaction of carbene 2Cl with pyridine. LFP (266 nm) of dienes 1Cl and 1F in CF(2)ClCFCl(2) with IR detection produces carbenes 2Cl and 2F with carbonyl vibrations at 1635 and 1650 cm(-1), respectively. In dioxane or THF solvent, LFP produces the corresponding ether ylides (5Cl, 5F) by capture of carbenes 2Cl and 2F. The ylides have broad carbonyl vibrations between 1560 and 1610 cm(-1). The addition of a small amount of dioxane in CFCl(2)CF(2)Cl extends the lifetime of the carbene. This observation, together with the ether-induced retardation of the rates of carbene capture by tetramethylethylene and pyridine, is evidence for solvation of the carbene by dioxane.     

壳聚糖在4种咪唑型离子液体中溶解性的研究

研究、比较了壳聚糖在4种咪唑型离子液体氯化1-丁基-3-甲基咪唑([BMIM]Cl)、1-丁基-3-甲基咪唑醋酸盐([ BMIM] Ac)、1-乙基-3-甲基咪唑醋酸盐([EMIM] Ac)和氯化1-烯丙基-3-甲基咪唑([AMIM] Cl)中的溶解性,提出了可能的溶解机理,并利用红外光谱(FTIR)、热重分析(TGA...     

A spectral study of the interaction of dioxygen with sublimed layers of manganese(ii)meso-tetraphenylporphyrinate

The low-temperature interaction of sublimed layers of manganese(ii)meso-tetraphenylporphyrinate (MnTPP) with O₂, which has previously been observed only in solutions and in an inert gas matrix, was found by electron absorption and IR spectroscopy. The coordination of O₂ with sublimed MnTPP layers is only partially reversible. Bands that can serve as IR-spectral markers characteristic of the high-spin Mn^II ion in MnTPP and its axial complexes were observed. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1551–1555, September, 2000.     

Structure and magnetic properties of (meso-tetraphenylporphinato)manganese(III) bis(dithiolato)nickelates

The crystal structures of [MnTPP]{Ni[S2C2H(CN)]2} [MnTPP = (meso-tetraphenylporphinato)manganese(III)] and [MnTPP]{Ni[S2C2(CN)2]2} have been determined. These salts possess trans-mu-coordination of S = 1/2 {Ni[S2C2H(CN)]2}*- and {Ni[S(2)C(2)(CN)(2)](2)}*- to Mn(III) and form parallel 1-D coordination polymer chains exhibiting nu(CN) at 2210 and 2200 and 2220 and 2212 cm(-1), respectively. The bis(dithiolato) monoanions are planar and bridge two cations with MnN distances of 2.339(16), and 2.394(3) A, respectively, which are comparable to related MnN distances observed for [MnTPP][TCNE].x(solvates). In addition, [MnTP'P]{Ni[S2C2(CN)2]2} {H2TP'P = meso-tetrakis[3,5-di-tert-butyl-4-hydroxyphenyl)porphyrin] and [MnTP'P(OH2)]{Ni[S2C2(CN)2]2} were prepared. The latter forms isolated paramagnetic ions. The room-temperature values of chiT for 1-D [MnTPP]{Ni[S2C2H(CN)]2}, [MnTPP]{Ni[S2C2(CN)2]2}, and [MnTP'P]{Ni[S2C2(CN)2]2} are 2.55, 3.28, and 2.86 emu K/mol, respectively. Susceptibility (chi) measurements between 2 and 300 K reveal weak antiferromagnetic interactions with theta= -5.9 and -0.2 K for [MnTPP]{Ni[S(2)C(2)H(CN)](2)} and [MnTPP]{Ni[S2C2(CN)2]2}, respectively, and stronger antiferromagnetic coupling of -50 K for [MnTP'P]{Ni[S2C2(CN)2]2} from fits of chi(T) to the Curie-Weiss law. The 1-D intrachain coupling, J(intra), of [MnTPP]{Ni[S2C2H(CN)]2} and [MnTPP]{Ni[S2C2(CN)2]2} was determined from modeling chiT(T) by the Seiden expression (H = -2JSi.Sj) with J/kB = -8.00 K (-5.55 cm(-1); -0.65 meV) for [MnTPP]{Ni[S2C2H(CN)]2}, J/kB = -3.00 K (-2.08 cm(-1); -0.25 meV) for [MnTP'P]{Ni[S2C2(CN)2]2}, and J/kB = -122 K (-85 cm(-1)) for [MnTP'P]{Ni[S2C2(CN)2]2}. These observed negative J(intra)/kB values are indicative of antiferromagnetic coupling. These materials order as ferrimagnets at 5.5, 2.3, and 8.0 K, for [MnTPP]{Ni[S2C2H(CN)]2}, [MnTPP]{Ni[S2C2(CN)2]2}, and [MnTP'P]{Ni[S2C2(CN)2]2}, respectively, based upon the temperature at which maximum in the 10 Hz chi'(T) data occurs. [MnTP'P]{Ni[S2C2(CN)2]2} has a coercivity of 17,700 Oe and remanent magnetizations of 7250 emu Oe/mol at 2 K and 17 Oe and 850 emu Oe/mol at 5 K; hence, upon cooling it goes from being a soft magnet to being a very hard magnet.     

用X-光电子能谱对热处理的四苯基铁卟啉化学修饰电极的研究

本文用XPS、DTA、和TG分析了解四苯基铁卟啉和四苯基铁卟啉化学修饰电极的热分解行为。由XPS谱图揭示了玻璃炭与四苯基铁卟啉之间的相互作用, 进而阐述了经热处理的四苯基铁卟啉化学修饰电极的表面结构与电催化稳定性的关系。从四苯基铁卟啉化学修饰电极的XPS价态谱发现Fe中心离子的3d电子在电极的电催化活性中的作用。     

A series of 3d-4f heterometallic frameworks comprising 2D lanthanide-organic layers and diverse Cu-complex pillars

Six novel 3D layer-pillared lanthanide-transition metal coordination polymers,LnCuX(IN)2(Ac)(H2O)(Ln = Tb,X = Br(1);Ln = Er,X = Cl(2)),[LnCuCl(IN)2(Ac)].H2O(Ln = Gd(3);Ln = Eu(4)),and [LnCu2Br2(IN)2(Ac)(H2O)].nH2O(Ln = Dy,n =0(5);Ln = Gd,n = 0.5(6))(IN = isonicotinate,Ac = acetate),have been obtained by linking Ln-organic layers and diverse Cu-complex pillars under hydrothermal conditions.1 and 2 are isostructural and formed by 2D Ln-IN-Ac layers and CuX(IN)2 pillars(X = Br(1),X= Cl(2));3 and 4 are isomorph...     

Spin-related electronic pathway through single molecule on Au(111)

Spin properties of organic molecules have attracted great interest for their potential applications in spintronic devices and quantum computing. Fe-tetraphenyl porphyrin (FeTPP) is of particular interest for its robust magnetic properties on metallic substrates. FeTPP is prepared in vacuum via on-surface synthesis. Molecular structure and spin-related transport properties are characterized by low-temperature scanning tunneling microscope and spectroscopy at 0.5 K. Density functional theory calculations are performed to understand molecular adsorption and spin distribution on Au(111). The molecular structure of FeTPP is distorted upon adsorption on the substrate. Spin excitations of FeTPP are observed on the Fe atom and high pyrrole groups in differential conductance spectra. The calculated spin density distribution indicates that the electron spin of FeTPP is mainly distributed on the Fe atom. The atomic transmission calculation indicates that electrons transport to substrate is mediated through Fe atom, when the tip is above the high pyrrole group.     

铁卟啉与氟尿嘧啶轴向配位热力学性质研究

氟尿嘧啶(Fu)是一种常用的抗代谢药物,在体内可转变为脱氧尿嘧啶核苷酸,抑制胸腺嘧啶核苷酸合成酶,从而阻止尿嘧啶脱氧核苷酸转变成胸腺嘧啶脱氧核苷酸,它的结构与肿瘤细胞所必需的尿嘧啶相类似,在同一系统酶中互相竞争,阻断代谢环节,影响DNA的生物合成,从而抑制了肿瘤细胞的生长.它对多种癌症都有较好的疗效,但具有一定的毒副作用^[1].这些毒副作用产生的机理目前尚不清楚.卟啉类化合物是人体中不可缺少的物质,具有许多特殊的生物效应^[2～11].若它们的含量异常,则会引发多种病变.     

Impact of ligand exchange in hydrogen production from cobaloxime-containing photocatalytic systems

Ligand exchange on the Co(dmgH)(2)(py)Cl water reduction catalyst was explored under photocatalytic conditions. The photosensitizer fluorescein was connected to the catalyst through the axially coordinated pyridine. While this two-component complex produces H(2) from water under visible light irradiation in the presence of triethanolamine (TEOA), it is less active than a system containing separate fluorescein and [Co(III)(dmgH)(2)(py)Cl] components. NMR and photolysis experiments show that the Co catalyst undergoes pyridine exchange. Interestingly, glyoximate ligand exchange was also observed photocatalytically and by NMR spectroscopy, thereby showing that integrated systems in which the photosensitizer is linked directly to the Co(dmgH)(2)(py)Cl catalyst may not remain intact during H(2) photogeneration. These studies have also given rise to insights into the catalyst decomposition mechanism.     

'Pincer' dicarbene complexes of some early transition metals and uranium

The complexes [(C-N-C)MX(n)(thf)(m)] with the 'pincer' 2,6-bis(imidazolylidene)pyridine, (C-N-C) = 2,6-bis(arylimidazol-2-ylidene)pyridine, aryl = 2,6-Pr(i)2C6H3, M = V, X = Cl, n = 2, m = 1 1a; M = Cr, X = Cl, n = 2, m = 0, 2a, X = Br, 2b; M = Mn, X = Br, n = 2, m = 0, 3; M = Nb, X = Cl, n = 3, m = 0, 4; and M = U, X = Cl, n = 4, m = 0, 5, were synthesised by (a) substitution of labile tmed (1a), thf (2a, 3, 5) or dme (4) by free (C-N-C) or by (b) reaction of the bisimidazolium salt (CH-N-CH)Br2 with {Cr[N(SiMe3)2]2(thf)2} followed by amine elimination (2b). Attempted alkylation of 1a, 2, 3a and 4 with Grignard or alkyl lithiums gave intractable mixtures, and in one case [reaction of 1a with (mesityl)MgBr] resulted in exchange of Cl by Br (1b). Oxidation of 1a or [(C-N-C)VCl3] with 4-methylmorpholine N-oxide afforded the trans-V(C-N-C)(=O)Cl2, 6, which by reaction with AgBF4 in MeCN gave trans-[V(C-N-C)(=O)(MeCN)2][BF4]2, 7. Reaction of 1a with p-tolyl azide gave trans-V(C-N-C)(=N-p-tolyl)Cl2 8. The complex trans-Ti(C-N-C)(=NBu(t))Cl2, 9, was prepared by substitution of the pyridine ligands in Ti(NBu(t))Cl2(py)3 by C-N-C.     

2-(2-苯并咪唑基)吡啶双核镉(Ⅱ)配合物的水热合成、晶体结构及荧光性质

通过水热反应,合成了2-(2-苯并咪唑基)吡啶(BMPY)镉(Ⅱ)配合物[Cd2Cl4(BMPY)2]。对它进行了元素分析、热重、红外光谱及电子光谱表征,并用X-射线单晶衍射测定了配合物的晶体结构。配体2-(2-苯并咪唑基)吡啶中的2个氮原子与3个氯原子与镉(Ⅱ)配位,形成五配位的畸变四角锥构型,2个配位镉(Ⅱ)离子通过双氯桥键结合成双核镉的配合物。该配合物通过分子间N-H…Cl,C-H…Cl氢键和π-π作用形成一维链状结构。热重-微分热重(TG-DTG)分析结果表明,[Cd2Cl4(BMPY)2]在320℃以下无分解反应,耐热性好。室温固态荧光测试显示,配合物在408.9 nm(λmax)处具有较强的荧光发射。     

Bis(arylimino)pyridine derivatives of Group 4 metals: preparation, characterization and activity in ethylene polymerization

Titanium tetrachloride reacts with 2,6-bis[(1-phenylimino)ethyl]pyridine, 1, and 2,6-bis[1-(2,6-diisopropylphenylimino)ethyl]pyridine, 2, giving the adducts of general formulae [Ti1Cl3]Cl, 3, and [Ti2Cl3]Cl, 6, the latter through the intermediacy of the covalently bonded [Ti2Cl4], 4. Heating 6 leads to reduction to the titanium(III) derivative [Ti2Cl3], 12, the latter characterized by X-ray diffraction methods. The reaction of [Ti1Cl3]Cl with a toluene solution of MAO proceeds with methylation at the ortho-position of the pyridine ring to give the titanium(iv) derivative [Ti(C22H21N3)Cl3], 8. The reaction of [Ti2Cl3]Cl with MAO gives a mixture of products containing [Ti2Cl2(OAlCl3)], 9. Compound 9, which has been prepared independently by reacting 6 with AlOCl, is a rare case of a compound containing the -OAlCl3 moiety, as shown by a single-crystal X-ray diffraction study. From the tetrachlorides of zirconium and hafnium with 1 or 2, the corresponding adducts [M(L)Cl4] have been obtained in high yields. These derivatives of Group 4 metals act as ethylene polymerization catalytic precursors: the substitution of the phenyl ring of the imino fragment strongly influences the catalytic activity which is 5,544 kg(PE) mol(Ti)(-1) h(-1) in the case of 3 and 267 kg(PE) mol(Ti)(-1) h(-1) with 6. Catalytic activity has been observed for zirconium and hafnium too, the activity decreasing from zirconium to hafnium, under comparable conditions.     

Solvent dependence of the structure and magnetic ordering of ferrimagnetic manganese(III) meso-tetraphenylporphyrin tetracyanoethenide, [MnTPP]+[TCNE]*-

Tetraphenylporphinatomanganate(III) tetracyanoethenide, [MnTPP][TCNE], is the prototype of a growing family of linear chain (1-D) coordination polymers that magnetically order as ferrimagnets. [MnTPP][TCNE].xS [S = PhMe (x = 2), 1,2-C(6)H(4)Me(2) (x = 1), 1,2-C(6)H(4)Cl(2) (x = 3), 1,2,4-C(6)H(3)Cl(3) (x = 2), and 1,3-C(6)H(4)Cl(2) (x = 2)] have been prepared and structurally and magnetically characterized. All form 1-D chain structures with intrachain Mn.Mn separations ranging from 9.202 to 10.218 A. The 173 K crystal structure of [MnTPP][TCNE].2PhMe has been rerefined, revealing that the [TCNE](*)(-) is 2-fold-disordered and coordinated to Mn(III) by a pair of trans cyano nitrogen atoms to form parallel one-dimensional chains. The two orientations of [TCNE](*)(-) are related by a 180 degrees rotation about the diagonal axis joining the trans nitrogen atoms bound to Mn(III). The major form has an occupancy of 83.3(4)% with a Mn-N(TCNE) distance of 2.328(3) A and a MnNC angle of 146.8(8) degrees. The minor form, with 16.7(4)% occupancy, has a Mn-N(TCNE) distance of 2.176(15) A and a MnNC angle of 152.3(39) degrees. Lattice packing and molecular bonding imply static as opposed to dynamic disorder. The magnetic properties depend on the type and quantity of the solvent present in the structure. Desolvation via heating in n-octane (127 degrees C), n-dodecane (216 degrees C), and/or vacuum thermolysis (175 degrees C) leads to numerous different desolvated materials with differing magnetic properties. At higher temperatures the magnetic susceptibility can be fit by the Curie-Weiss expression, chi varies with (T - theta)(-1), with theta = 44, 52, 72, 55, and 77 K for the toluene, 1,2-xylene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, and 1,2,4-trichlorobenzene solvates, respectively. The T(c)'s were taken as the maximum in 10 Hz chi'(T) and are 7.8, 9.2, 11.3, 10.8, and 8.2 K for the PhMe, 1,2-xylene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, and 1,2,4-trichlorobenzene solvates, respectively. Upon desolvation the T(c)'s increase for the PhMe, 1,2-xylene, 1,2,4-trichlorobenzene solvates and decrease for the 1,2- and 1,3-dichlorobenezene solvates. The compounds show one-dimensional ferrimagnetic exchange behavior at high temperatures with intrachain exchange of J/k(b) = -63, -99, -234, -100, and -200 K for toluene, 1,2-xylene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, and 1,2,4-trichlorobenzene solvates, respectively, as determined from fits to the Seiden expression, which models isolated 1-D interactions among alternating S = 2 classical and S = (1)/(2) quantum spins. For variation in the temperature at which the peak occurs per decade of frequency, phi, (DeltaT(f)/T(f))/Delta(log omega) is 0.167, 0.168, 0.066, 0.171, and 0.024 for toluene, 1,2-xylene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, and 1,2,4-trichlorobenzene, respectively, typical of spin glass behavior. Since [TCNE](*)(-) is only disordered for the PhMe solvate and all five solvates exhibit spin glass behavior, the spin glass behavior cannot be attributed to this disorder.     

Synthesis and characterization of diorganohydrazido(2-) tungsten complexes

Diorganohydrazido(2-) complexes of tungsten (L)Cl4W(NNR2) [R2=Me2, Ph2, -(CH2)5-; L=CH3CN, pyridine] were synthesized by reacting the corresponding 1,1-diorganohydrazine with WCl6, followed by reaction with acetonitrile or pyridine. Crystallographic structure determination of (CH3CN)Cl4W(NNMe2) and (CH3CN)Cl4W(NNPh2) allows a comparison of the structural features of the diorganohydrazido(2-) functionality with varying substituents. Mass spectrometry, thermogravimetric analysis, and preliminary chemical vapor deposition experiments were performed to determine the viability of these complexes as single-source precursors for deposition of WNx and WNxCy films.     

Electronic structure of some substituted iron(II) porphyrins. Are they intermediate or high spin?

The electronic structure of some substituted, four-coordinate iron(II) porphyrins has been investigated with DFT methods. These systems include iron tetraphenylporphine (FeTPP), iron octamethyltetrabenzporphine (FeOTBP), iron tetra(alpha,alpha,alpha,alpha-orthopivalamide)phenylporphine (FeTpivPP, also called "picket fence" porphyrin), halogenated iron porphyrins (FeTPPXn, X=F, Cl; n=20, 28), and iron octaethylporphine (FeOEP). A number of density functionals were used in the calculations. Different from the popular, intermediate-spin FeTPP, the ground states of FeOTBP, FeTPPCl28, and FeTPPF20betaCl8 are predicted to be high spin. The calculated result for FeOTBP is in agreement with the early experimental measurement, thereby changing the previous conclusion drawn from the calculations with only the BP functional (J. Chem. Phys. 2002, 116, 3635). But FeTpivPP might have an intermediate-spin ground state, a conclusion that is different from the "experimental" one. With a notably expanded Fe-N bond length, FeOEP might exist as an admixed-spin (S=1, 2) state. We also calculated the electron affinities (EAs) for the various iron porphyrins and compared them to experiment. On the basis of the calculated trends in the EAs and in the orbital energies, the experimental EAs for FeTpivPP, FeTPPF20, and FeTPPCl28 may be too small by 0.4-0.5 eV.