表面活性剂增敏铍试剂Ⅱ荧光法测定痕量锰

在碱性条件下，Ｍｎ（Ⅱ）与铍试剂Ⅱ形成１；２的荧光络合物，其荧光峰为λｅｘ＝λｅｍ＝３６７／４６７（ｎｍ），表面活性剂十二烷基苯磺酸钠对体系具有强烈增敏作用，基于此建立了痕量锰的测定方法。本文研究了测定的最佳条件，即０．０１％铍试剂Ⅱ４．０ｍＬ，０．１ｍｏｌ／ＬＮａＯＨ６．０ｍＬ，１％ＳＤＢＳ ４．０ｍＬ，反应温度为９０℃，时间１０ｍｉｎ，线性范围为０－１６０μｇ／Ｌ，回归方程Ｘ（μｇ／Ｌ）＝２．     

混合三烃基锡有机酸酯化合物构效关系 （Ⅰ）二环己基－甲基－2，4－二溴－β－甲基苯氧乙酸锡酯 及二环己基－甲基－2－甲氧基－4－丙烯基苯氧乙酸锡酯的晶体结构和分子结构

报道２，４－Ｂｒ２Ｃ６Ｈ３ＯＣＨ（ＣＮ３）ＣＯ２Ｓｎ（Ｃ６Ｈ１１）２ＣＵ３（１）和２－ＯＣＨ３－４－ＣＨ３ＣＨ＝ＣＨＣ６Ｈ３ＯＣＨ２ＣＯ２Ｓｎ（Ｃ６Ｈ１１）２ＣＨ３（Ｈ２Ｏ）（Ⅱ）的晶体结构和分子结构。（Ⅰ）单斜晶系，空间群Ｐ２１／ｃ，ａ＝１３．０６７（３），ｂ＝１０．５９４（３），ｃ＝１８．１５７（４），β＝１０６．９９（２）°，Ｚ＝４，Ｄｃ＝１．６７２ｇ／ｃｍ３，Ｖ＝２４０３．７３，μ＝４３．７３１ｃｍ－１，Ｍｒ＝６２２．９９，Ｆ（０００）＝１２３２；（Ⅱ）单斜晶系，空间群Ｐ２１／ｎ，ａ＝１０．４０９（１），ｂ＝　１２．５７０（２），ｃ＝２０．６６４（２），β＝８３．５１（１）°，Ｚ＝４，Ｄｃ＝１．２８１ｇ／ｃｍ３，Ｖ＝２６８６．４Ａ３，μ＝９．７６１ｃｍ－１，Ｍｒ＝５３９．２８，Ｆ（０００）＝１１２０．最后的偏离因子，化合物（Ⅰ）Ｒ＝０．０４６，Ｒω＝０．０４６；化合物（Ⅱ）Ｒ＝０．０４９，Ｒω＝０．０４７。晶体结构解析表明，化合物（Ⅰ）和（Ⅱ）中的锡均被配体的３个碳和２个氧原子配位，配位原子呈畸变三角双锥构型；化合物中的环己基均为椅式构象；化合物（Ⅱ）中，配位水分子和另一分子的羰基氧与芳环上的甲基氧?     

Mn－Ag／γ－Al_2O_3催化剂中氧的性能

本文运用ＴＰＲ、ＴＰＤ－ＭＳ、ＸＲＤ等技术研究了Ｍｎ－Ａｇ／γ－Ａｌ_２Ｏ_３催化剂的还原性能和再氧化能力．结果表明，Ｍｎ－Ａｇ／γ－Ａｌ_２Ｏ_３中银物相由Ａｇ￣０和Ａｇ_２Ｏ组成，锰物相由β－ＭｎＯ_２和Ｍｎ２Ｏ_３组成．Ｍｎ／γ－Ａｌ_２Ｏ_３催化剂的ＴＰＲ有二个还原峰，分别是ＭｎＯ_２和Ｍｎ_２Ｏ_３的还原．Ａｇ促使ＭｎＯ_２和Ｍｎ_２Ｏ_３的还原明显向低温方向移动，而且ＭｎＯ_２和Ｍｎ_２Ｏ_３的还原峰融合成一个还原峰．Ｍｎ－Ａｇ／γ－Ａｌ_２Ｏ_３的ＴＰＤ有三个脱氧峰，随着Ａｇ含量增加，峰Ⅰ向高温方向移动，Ｍｎ￣（４＋）２ｐ３／２的电子结合能增加，并且催化剂的再氧化能力增强．催化剂ＣＯ的氧化活性与催化剂的再氧化能力有很好的对应关系．     

（四甲基二硅撑）二（3－三甲硅基环戊二烯基）四羰基二铁及其相关化合物的合成及结构

１，２－二（三甲硅基环戊二烯基）四甲基二硅烷与Ｆｅ（ＣＯ）_５在二甲苯中于１０５～１１０℃反应除分离到少量标题化合物（Ｍｅ_２ＳｉＳｉＭｅ_２）［η－（３－Ｍｅ_３ＳｉＣ_５Ｈ_３Ｆｅ（ＣＯ）］_２（μ－ＣＯ）_２（５）外，主要是生成了脱Ｍｅ_３Ｓｉ基的产物（Ｍｅ_２ＳｉＳｉＭｅ_２）［η－Ｃ_５Ｈ_４Ｆｅ（ＣＯ）］_２（μ－ＣＯ）_２（１）及１的热重排异构体［Ｍｅ_２ＳｉＣ５Ｈ４－Ｆｅ（ＣＯ）_２］_２（２）．将５的二甲苯溶液加热回流１８ｈ，则转化为其异构体［Ｍｅ_２Ｓｉ（Ｍｅ_３ＳｉＣ_５Ｈ_３）Ｆｅ（ＣＯ）_２］_２（６）．脱硅基发生在由相应反应物制备５的过程中。且脱硅基是与反应物中（Ｍｅ_２ＳｉＳｉＭｅ_２）桥的存在有关．５的晶体结构经Ｘ射线衍射测定属单斜晶系，Ｐ２_１／ｍ空间群，晶体学数据：ａ＝０．６７８０（１）ｎｍ，ｂ＝２．２３０３（９）ｎｍ，ｃ＝０．９９８８（１）ｎｎ，；β＝９８．９６（１）°，Ｖ＝１．４９６０ｎｍ~３．Ｚ＝２，Ｄ_ｃ＝１．３６ｇ／ｃｍ~３．     

MoO3/TiO2-Al2O3对H2S吸附的XPS研究

应用ＸＰＳ对ＭｏＯ３／ＴｉＯ２－Ａｌ２Ｏ３体系的ＭｏＯ３在ＴｉＯ２－Ａｌ２Ｏ３载体上的存在状态及其对Ｈ２Ｓ的吸附和脱附性能进行了表征，结果表明：ＭｏＯ３在ＴｉＯ２－Ａｌ２Ｏ３表面存在分散状态的不同，这导致了对Ｈ２Ｓ吸附性能的不同，在相同的条件下，吸附剂的０．１５ｇＭｏＯ３／ｇＴｉＯ２－Ａｌ２Ｏ３时具有最大载硫量，且随吸附温度的升高载硫量也增加，达饱和对Ｓ／Ｍｏ原子比接近１，较好的氧化脱附温度为１５     

CuO／γ－Al_2O_3中热稳定助剂作用的探讨

用等量共浸法和分浸法制备了含Ｃａ、Ｓｒ、Ｂａ、Ｍｇ、Ｚｒ和Ｌａ助剂的ＣｕＯ／γ－Ａｌ_２Ｏ_３催化剂（ＣｕＯ／Ａｌ_２Ｏ_３＝８ｗｔ％，Ｍ／Ｃｕ（原子比）＝０．１５，Ｌａ／Ｃｕ＝０．３５）．用ＸＲＤ和ＸＰＳ等考察了在高温７５０℃、９５０℃和１０５０℃老化后的相结构和ＣＯ氧化活性，实验表明所有助剂均有不同程度的抗烧结和抗相变作用。其中Ｌａ、Ｃａ和Ｚｒ的效果最好。分浸法比共浸法好。在９５０℃老化后，ＣｕＡｌ_２Ｏ_４和α－Ａｌ_２Ｏ_３同步产生；随老化温度增高，ＣＯ氧化活性有所下降。分浸法制备的含Ｚｒ样品在９５０℃老化后活性最高。从γ－Ａｌ_２Ｏ_３缺陷尖晶石特征及高温脱结构水过程，探讨了助剂抑制α－Ａｌ_２Ｏ_３生成的原因。     

含硫、氮Schiff碱配合物—二水二分之一二甲基亚砜醋酸四邻香草醛缩胺基硫脲合镉（Ⅱ）的合成及晶体结构

Ｘ射线单晶衍射结果表明，三核镉配合物Ｃｄ３［ＣＨ３Ｏ（Ｏ）Ｃ６Ｈ３ＣＨ＝ＮＮＨＣ（Ｓ）ＮＨ２］４·［ＣＨ３ＣＯＯ］２·１／２［ＣＨ３Ｓ（Ｏ）ＣＨ３］·２Ｈ２Ｏ为单斜晶系，空间群为Ｃ２／ｃ，ａ＝３．４２１４（４），ｂ＝１．１５８１（２），ｃ＝１．７９３２（５）ｎｍ，β＝１１９．７６（１）°，Ｖ＝６．１６８ｎｍ３，Ｍｒ＝１４２７．４３，Ｚ＝４，Ｄｃ＝１．５４ｇ／ｃｍ３，μ＝１２．４８ｃｍ（－１），Ｆ（０００）＝２８６０，最后偏离因子Ｒ＝０．０６６．     

Ag／γ－Al_2O_3催化剂的TPR和TPD研究

本文运用ＴＰＤ－ＭＳ、ＴＰＲ等方法研究了Ａｇ／γ－Ａｌ_２Ｏ_３催化剂的氧脱附和还原性能。结果表明，Ａｇ／γ－Ａｌ_２Ｏ_３催化剂表面银物相由Ａｇ０和Ａｇ＋（Ａｇ２Ｏ）组成，其中Ａｇ＋所占比例随负载量增加而减少。Ａｇ／γ－Ａｌ_２Ｏ_３催化剂有三个脱氧峰，并且随着Ａｇ负载量的增加，脱氧峰从高温向低温依次出现。低温脱氧峰（３７０℃）归属为结晶态Ａｇ２Ｏ的分解，高温脱氧峰（６５０和８００℃）为分散在γ－Ａｌ_２Ｏ_３表面并且与Ａｌ_２Ｏ_３发生相互作用的Ａｇ_２Ｏ的分解。ＴＰＲ有三个还原峰；高温峰（２３０℃）为结晶态Ａｇ_２Ｏ的还原，低温峰（１００和１２０℃）为分散在γ－Ａｌ_２Ｏ_３表面的Ａｇ_２Ｏ的还原。     

三环己基锡O,O‘—二（4—氯苯基）—二硫代磷酯酯和二丁基锡双（O,O’—二…

三环己基锡Ｏ，Ｏ’－二（４－氯苯基）二硫代磷酸酯（Ｉ），Ｃ３０Ｈ４１Ｃｌ２（Ｏ２ＰＳ２Ｓｎ，Ｍｒ＝７１８．３６，单斜晶系，Ｐ２１／ｎ，ａ＝１６．１５１（２），ｂ＝９．４１５９（１），ｃ＝２２．９８７（３），Ａ，β＝１０５．６９（１）°，Ｚ＝４，Ｄｃ＝１．４１８ｇ．ｃｍ＾－３，Ｒ＝０．０６３；二丁基锡双（Ｏ，Ｏ’－二（４－甲基苯基）二硫代磷酯酯（Ⅱ），Ｃ３６Ｈ４６Ｏ４Ｐ２Ｓ４Ｓｎ，Ｍｒ＝８５１．６６     

Ce2O—TiO2／SiO2的制备及除氟性能研究

以ＳｉＯ２为基质，ＣｅＯ２ＴｉＯ２为包覆物质，采用溶胶凝胶法制备ＣｅＯ２ＴｉＯ２／ＳｉＯ２表面复合物，并对所制复合物进行除氟测试。用扫描电镜（ＳＥＭ）观察表面形貌，讨论实验环境、试剂用量等因素对ＣｅＯ２ＴｉＯ２／ＳｉＯ２制备及除氟性能的影响，结果表明：ｎＴｉ（ＯＣ４Ｈ９）４／ｎＣｅＣｌ３·７Ｈ２Ｏ＝１、ｎＣＨ３ＣＯＯＨ／ｎＴｉ（ＯＣ４Ｈ９）４＝４５、ｎＣ３Ｈ８Ｏ３／ｎＴｉ（Ｏ４Ｈ９）４＝０３、ＲＨ＝９５％，热处理温度１１０℃时，所制ＣｅＯ２ＴｉＯ２／ＳｉＯ２对Ｆ－的吸附容量（ｑ）为２１４ｍｇ／ｇ，去除率（Ｅ）为８５６％。     

The History of Artificial Ultramarine (1787–1844): Science,Industry and Secrecy

Abstract

Between 1826 and 1828 three ways of synthesising artificial ultramarine were found independently in Toulouse, Tübingen and Meissen. This paper is about the scientific development that led up to these events, the industrial production and marketing of ultramarine, and the roles played by Jean-Baptiste Guimet, Christian Gottlob Gmelin, Friedrich August Köttig, Carl Leverkus and Thomas Leykauf. Special attention is paid to the chemical analyses of lapis lazuli, natural ultramarine and the blue residues from soda furnaces prior to 1824, as well as the crucial roles played by chemical education, laboratory experiments and the scientific background of the early ultramarine manufacturers.     

Identification of the EPR signal of S₂⁻ in green ultramarine pigments

Green and blue ultramarine pigments are characterized by the sodalite structure Na(6)(Al(6)Si(6)O(24)) and colored inserted species. These chromophores are sulfur species: S(3)(-) (blue) and S(2)(-) (yellow). Both radicals are encapsulated inside the β-cages. They contribute to the EPR spectrum of ultramarine pigments. The well-known strong EPR signal observed in all ultramarine pigments Continuous-Wave (CW) spectra has long been assigned to S(3)(-) (g = 2.029). In contrast, the S(2)(-) contribution is still subject to controversy because its signal in ultramarine pigments was not resolved even at low temperature in CW-EPR experiments. In this study, we identify unambiguously for the first time by CW-EPR and field sweep-echo detected (FS-ED) EPR the signal of S(2)(-) in ultramarine pigments and we determine its tensor components: g(1) = 2.69(6), g(2) = 2.03(4) and g(3) = 1.86(4).     

Characterization of lapis lazuli and corresponding purified pigments for a provenance study of ultramarine pigments used in works of art

In this paper, we propose an analytical methodology for attributing provenance to natural lapis lazuli pigments employed in works of art, and for distinguishing whether they are of natural or synthetic origin. A multitechnique characterization of lazurite and accessory phases in lapis lazuli stones from Afghan, Siberian and Chilean quarries, on the pigments obtained by their purification, and on synthetic ultramarine pigments was performed. According to the results obtained, infrared spectroscopy is not a suitable technique for distinguishing the provenance of lapis lazuli, but a particular absorbance band makes it relatively easy to determine whether it is of natural or synthetic origin. On the other hand, EDS elemental composition and XRD patterns show the presence of specific mineral phases associated with specific lapis lazuli sources, and can be used to distinguish the provenance of the stones as well as—albeit to a lesser extent—the corresponding purified blue pigments. In contrast, FEG-SEM observations clearly show different stone textures depending on their provenance, although these distinctive features do not persist in the corresponding pigments. PCA analyses of EDS data allow Afghan lapis lazuli stone to be distinguished from Chilean and Siberian ones, and can distinguish between the pigments resulting from their purification as well as synthetic blue ones. Although this methodology was developed using a limited number of samples, it was tested on lapis lazuli pigments collected from three paintings (from the fourteenth to sixteenth centuries) in order to perform a preliminary validation of the technique, and based on the results, the provenance of the blue pigments employed in those artworks is proposed. Finally, upon analytically monitoring the process of purifying lapis lazuli to obtain the corresponding pigments, it was found that ion-exchange reactions occur between the alkali modifiers of silicate/aluminosilicate phases and free carboxylic acids present in the doughy mixture of natural terpenes and ground stone, namely pastello. These reactions favor (i) the retention of silicate phases in the organic mixture and (ii) the selective extraction of lazurite due to the formation of Br?nsted acidic sites [Al(OH)Si], which are responsible for its high hydrophilicity in comparison to the one of the other species present in the lapis lazuli stone.     

Multitechnique characterization of lapis lazuli for provenance study

Lapis lazuli is one of the oldest precious stone, being used for glyptic as early as 7,000 years ago: jewels, amulets, seals, and inlays are examples of objects produced using this material. Only a few sources of lapis lazuli exist in the world due to the low probability of geological conditions in which it can form, so that the possibility to associate the raw material to man-made objects helps to reconstruct trade routes. Since art objects produced using lapis lazuli are valuable, only nondestructive investigations can be carried out to identify the provenance of the raw materials. Ionoluminescence (IL) is a good candidate for this task. Similar to cathodoluminescence (CL), IL consists in the collection of luminescence spectra induced by megaelectronvolt ion (usually protons) irradiation. The main advantage of IL consists in the possibility of working in air while measuring simultaneously the composition of major and trace elements by means of complementary ion beam analysis techniques like particle-induced X-ray emission (PIXE) or particle-induced gamma-ray emission (PIGE). In the present work, a systematic study of the luminescence properties of lapis lazuli under charged particle irradiation is reported. In the first phase, a multitechnique approach was adopted (CL, scanning electron microscopy with microanalysis, micro-Raman) to characterize luminescent minerals. This characterization was propaedeutic for IL/PIXE/PIGE measurements carried out on significant areas selected on the basis of results obtained previously. Criteria to identify provenance of lapis lazuli from four of the main sources (Afghanistan, Pamir Mountains in Tajikistan, Chile, and Siberia) were proposed.     

Models of the cytochromes: crystal structures and EPR spectral characterization of low-spin bis-imidazole complexes of (OETPP)Fe(III) having intermediate ligand plane dihedral angles

The preparation, EPR spectra, and crystal structures of octaethyltetraphenylporphyrinatoiron(III) having two imidazole, N-benzylimidazole, and N-methylimidazole axial ligands are reported, [(OETPP)Fe(HIm)2]Cl, [(OETPP)Fe(N-BzIm)2]Cl, and [(OETPP)Fe(N-MeIm)2]Cl. Despite large variation in axial ligand size, the unit cell parameters for all complexes are very similar; each structure has the same basic motif, with large voids formed by the extended porphyrin framework (filled by ordered or disordered axial ligands and disordered solvent), which allows differently sized ligands to fit within the same cell dimensions. Each porphyrin core adopts a saddled conformation with absolute value(deltaC(beta)) = 1.13-1.15 A. The dihedral angles between axial ligand planes, delta phi, are far from being either ideal parallel or perpendicular: 30.1 degrees, 57.2 degrees for [(OETPP)Fe(HIm)2]Cl (molecules 1 and 2), 56.8 degrees for [(OETPP)Fe(N-BzIm)(2)]Cl, and 16.0 degrees, 44.6 degrees, 59.6 degrees, and 88.1 degrees for [(OETPP)Fe(N-MeIm)2]Cl, which has disordered axial ligands. Among the complexes of this study, an axial ligand delta phi of 56.8 degrees is found to be the largest "parallel" angle (as defined by the observation of a normal rhombic or Type II EPR signal (N-BzIm, g = 3.08, 2.19, 1.31)), while 57.2 degrees is found to be the smallest "perpendicular" delta phi (as defined by the observation of a "large gmax" or Type I EPR signal (HIm, gmax = 3.24)). From the results of this study, it is clear that the size of the largest g for Types I and II complexes varies continuously, with no break between the two. While the switch in EPR signal type, from Type II to Type I, appears to be very sharp in this study, this may be somewhat artificial based upon limited numbers of examples and the required saddle distortion of the (OETPP)Fe(III) complexes. However, in comparison to several proteins with dihedral angles near 60 degrees and Type II EPR spectra, we may conclude that the switch in EPR signal type occurs near 57 degrees +/- 3-5 degrees.     

Influence of mixed thiolate/thioether versus dithiolate coordination on the accessibility of the uncommon +I and +III oxidation states for the nickel ion: an experimental and computational study

Sulfur-rich nickel metalloenzymes are capable of stabilizing Ni(I) and Ni(III) oxidation states in catalytically relevant species. In an effort to better understand the structural and electronic features that allow the stabilization of such species, we have investigated the electrochemical properties of two mononuclear N(2)S(2) Ni(II) complexes that differ in their sulfur environment. Complex 1 features aliphatic dithiolate coordination ([NiL], 1), and complex 2I is characterized by mixed thiolate/thioether coordination ([NiL(Me)]I, 2I). The latter results from the methylation of a single sulfur of 1. The X-ray structure of 2I reveals a distorted square planar geometry around the Ni(II) ion, similar to what was previously reported by us for 1. The electrochemical investigation of 1 and 2(+) shows that the addition of a methyl group shifts the potentials of both redox Ni(II)/Ni(I) and Ni(III)/Ni(II) redox couples by about 0.7 and 0.6 V to more positive values. Through bulk electrolyses, only the mononuclear dithiolate [Ni(I)L](-) (1(-)) and the mixed thiolate/thioether [Ni(III)L(Me)](2+) (2(2+)) complexes were generated, and their electronic properties were investigated by UV-vis and EPR spectroscopy. For 1(-) (Ni(I), d(9) configuration) the EPR data are consistent with a d(x(2))(-)(y(2)) based singly occupied molecular orbitals (SOMOs). However, DFT calculations suggest that there is also pronounced radical character. This is consistent with the small g-anisotropy observed in the EPR experiments. The spin population (Mulliken analysis) analysis of 1(-) reveals that the main contribution to the SOMO (64%) is due to the bipyridine unit. Time dependent density functional theory (TD-DFT) calculations attribute the most prominent features observed in the electronic absorption spectrum of 1(-) to metal to ligand charge transfer (MLCT) transitions. Concerning 2(2+), the EPR spectrum displays a rhombic signal with g(x) = 2.236, g(y) = 2.180, and g(z) = 2.039 in CH(3)CN. The g(iso) value is larger than 2.0, which is consistent with metal based oxidation. The unpaired electron (Ni(III), d(7) configuration) occupies a Ni-d(z(2)) based molecular orbital, consistent with DFT calculations. Nitrogen hyperfine structure is observed as a triplet in the g(z) component of the EPR spectrum with A(N) = 51 MHz. This result indicates the coordination of a CH(3)CN molecule in the axial position. DFT calculations confirm that the presence of a fifth ligand in the coordination sphere of the Ni ion is required for the metal-based oxidation process. Finally, we have shown that 1 exhibits catalytic reductive dehalogenation activity below potentials of -2.00 V versus Fc/Fc(+) in CH(2)Cl(2).     

EPR parameters and impurity structures for Cr3+ ions in KSc(MoO4)2, RbIn(MoO4)2 and RbSc(MoO4)2 crystals

The calculations of EPR parameters (g factors g||, g(perpendicular) and zero-field splitting D) related to the impurity structures have been made from the high-order perturbation formulas for Cr(3+) ions in trigonal KSc(MoO(4))(2), RbIn(MoO(4))(2) and RbSc(MoO(4))(2) crystals. It is found that the MO(6) octahedra in these crystals change from the trigonal elongation in the pure crystals to the trigonal compression in the impurity centers. The results are discussed.     

An EPR and 1H NMR active mixed-valence manganese (III/II/III) trinuclear compound

A mixed-valence Mn(III)-Mn(II)-Mn(III) trinuclear complex of stoichiometry MnIIIMnIIMnIII(Hsaladhp)2(Sal)4.2CH3CN (1), where H3saladhp is a tridentate Schiff-base ligand, has been structurally characterized with X-ray crystallography. The Mn(III)Mn(II)Mn(III) angles are strictly 180 degrees as required by crystallographic inversion symmetry. The complex is valence-trapped with two terminal Mn(III) ions in a distorted square pyramidal geometry. The Mn(III)...Mn(II) separation is 3.495 A. The trinuclear complex shows small antiferromagnetic exchange J coupling. The magnetic parameters obtained from the fitting procedure in the temperature range 10-300 K are J1 = -5.7 cm-1, g = 2.02, zJ = -0.19 cm-1, and R = 0.004. The EPR spectrum was obtained at 4 K in CHCl3 and in tetrahydrofuran glasses. The low-field EPR signal is a superposition of two signals, one centered around g = 3.6 and the other, for which hyperfine structure is observed, centered around g = 4.1 indicating an S = 3/2 state. In addition, there is a 19-line signal at g = 2.0. The multiline signal compares well with that observed for the S2 or S0* states of the oxygen-evolving complex. 1H NMR data reveal that the trinuclear compound keeps its integrity into the CHCl3 solution. Crystal data for complex 1: [C54H52N4O18Mn3], M = 1209.82, triclinic, space group P1, a = 10.367(6) A, b = 11.369(6) A, c = 13.967(8) A; alpha = 112.56(1) degree, beta = 93.42(2) degrees, gamma = 115.43(1) degree, Z = 1.     

Magnetic resonance spectroscopic investigations of the electronic ground and excited states in strongly nonplanar iron(III) dodecasubstituted porphyrins

A series of axially ligated complexes of iron(III) octamethyltetraphenylporphyrin, (OMTPP)Fe(III), octaethyltetraphenylporphyrin, (OETPP)Fe(III), its perfluorinated phenyl analogue, (F(20)OETPP)Fe(III), and tetra-(beta,beta'-tetramethylene)tetraphenylporphyrin, (TC(6)TPP)Fe(III), have been prepared and characterized by (1)H NMR spectroscopy: chloride, perchlorate, bis-4-(dimethylamino)pyridine, bis-1-methylimidazole, and bis-cyanide. Complete spectral assignments have been made using 1D and 2D techniques. The temperature dependences of the proton resonances of the complexes show significant deviations from simple Curie behavior and evidence of ligand exchange, ligand rotation, and porphyrin ring inversion at ambient temperatures. At temperatures below the point where dynamics effects contribute, the temperature dependences of the proton chemical shifts of the complexes could be fit to an expanded version of the Curie law using a temperature-dependent fitting program developed in our laboratory that includes consideration of a thermally accessible excited state. The results show that, although the ground state differs for various axial ligand complexes and is usually fully consistent with that observed by EPR spectroscopy at 4.2 K, the excited state often has S = (3)/(2) (or S = (5)/(2) in the cases where the ground state has S = (3)/(2)). The EPR spectra (4.2 K) of bis-4-(dimethylamino)pyridine and bis-1-methylimidazole complexes show "large-g(max)" signals with g(max) = 3.20 and 3.12, respectively, and the latter also shows a normal rhombic EPR signal, indicating the presence of low-spin (LS) (d(xy))(2)(d(xz),d(yz))(3) ground states for both. The bis-cyanide complex also yields a large-g(max) EPR spectrum with g = 3.49 and other features that could suggest that some molecules have the (d(xz),d(yz))(4)(d(xy))(1) ground state. The EPR spectra of all five-coordinate chloride complexes have characteristic features of predominantly S = (5)/(2) ground-state systems with admixture of 1-10% of S = (3)/(2) character.     

Synthesis, spectroscopy, and electrochemistry of copper(II) complexes with N,N'-bis(3,5-di-t-butylsalicylideneimine)polymethylenediamine ligands

Bulky salen CuL(x) derived from aliphatic polymethylene diamines, H(2)N-(CH(2))(x)-NH(2), where n = 2-6, and 3,5-di-t-butylsalicylaldehyde (H(2)L(x)) and some corresponding tetrahydrosalan complexes (CuL(x)') have been synthesized and characterized by their IR, UV-vis absorption and EPR spectra, by magnetic moments and by cyclic voltammetry in acetonitrile (for H(2)L(x)) and DMF (for CuL(x)). Complexes CuL(x) and CuL(x)' are magnetically normal (mu(exp) = 1.83-1.91 mu(B)). EPR spectra CuL(x) characterized by the axial g and A(Cu) tensors with g parallel > g perpendicular and without (14)N-shf resolution in CHCl(3)/toluene at 300 and 150K. The CV studies on acetonitrile solutions of H(2)L(x) revealed a well-defined quasi-reversible redox wave at E(1/2) = 0.95-1.15 V versus Ag/AgCl but CV of the CuL(x) complexes in DMF exhibit weak pronounced irreversible oxidation waves at E(pa)(1) = 0.51 - 098 V and E(pa)(2) = 1.16 - 1.33 V attributable to metal centered Cu(II/III) and ligand centered CuL(x)/CuL(x)*+ couples, respectively. A poorly defined wave was observed for the quasi-reversible reduction Cu(II)/Cu(I) at potentials less than -1.0 V.