谈氢键效应在某些前沿领域研究中的重要作用

目前，关于氢键本质的探讨已进一步深入到生命科学等前沿领域。本文以dnA的结构，顺铂的抗癌机制，非对映异构光学活性络合物间的手性识别，络合物间电子转移反应的立体选择性为例，从新的角度阐述了氢键效应在某些前沿领域研究中的重要作用。）；而当阳离子以特征C轴接近阴离子时，有利缔合离子对却为异手性的（Λ-△或△-Λ）；当阳离子兼有C3与C2特征时，则有利缔合的方式不定（或为同手性或为异手性）。由此，MIyOSHI等提出了四种手性识别模型（图2）。实验中，通常用光学活性络合物手性试剂来拆分某一外消旋络合物，一般情况下络阴阳离子间将按有利缔合离子对的方式，优先生成在三维空间无限延伸的非对映异构难溶盐晶体（例如［Λ-CO（En）3］［△-CO（OX）2（gly）］I·H2O，图3），而不利缔合离子对则以易溶盐形式留在溶液中。MIyOSHI模型可以解释许多络合物间手性识别的结果，但由于片面强调络阳离子的对称性而忽略了络阴离子的对称性对手性识别存在的潜在影响，不可避免地存在某些局限性。TATEHATA等又根据实验事实，进一步提出了考虑阴离子结构特征的氢键识别模式［8］。2.络合物间电子转移反应立体选择性中的氢键效应络合物间电子

Absolute Asymmetric Synthesis and Resolution Mechanism of Chiralcis-bromoamminebis(ethylenediamine)cobalt(III) Bromide

分别用绝对不对称合成和改进的拆分方法制备标题配合物!-(+)D-cis-[CoBr(NH3)(en)2]Br2(1)和"-(-)D-cis-[CoBr(NH3)(en)2]Br2(2),以及制备了cis-[CoBr(NH3)(en)2]Br·22H2O(3)(en=1,2-乙二胺).用元素分析、差热-热重、旋光度、UV-Vis、CD光谱等对产物进行了表征.通过CD光谱法获得了绝对不对称合成Co(III)配合物的产物ee值分布图.当利用绝对不对称合成得到的手性Co(III)配合物去“逆向拆分”外消旋溴代樟脑磺酸铵[NH4(dl-BCS)]时只获得部分拆分,初步认为这与交互拆分过程中阴阳离子之间的有效手性识别有关,对于手性Co(III)配合物的绝对不对称合成还提出了一个新的反应机理,即“催化-结晶诱导”机理.The absolute asymmetric synthesis of the title complexes ?撰-(+)D-cis-[CoBr(NH3)(en)2]Br2(1) and ?驻-(-)D-cis-[CoBr(NH3)(en)2]Br2(2)(en=1,2-ethylenediamine) as well as the improved optical resolution of cis-[CoBr(NH3)(en)2]Br2·2H2O(3) are described in detail. The products were characterized by means of elemental analysis, TG-DTA, optical rotation, UV-Vis, and CD spectra. The distribution of enantiomeric excess(ee) of cis-[CoBr(NH3)(en)2]Br2 in the absolute asymmetric synthesis was obtained by the measurements of their CD spectra. It was found that the complete resolution of rac-cis-[CoBr(NH3)(en)2]Br2·2H2O was achieved by use of NH4(d-BCS) (ammonium d-α-bromocamphor-π-sulfonate) or NH4(l-BCS) while NH4(dl-BCS) could only be partially resolved by chiral cis-[CoBr(NH3)(en)2]Br2 at the same condition. It is deduced that there are notable differences in the chiral discrimination of the reciprocal resolution between cis-[CoBr(NH3)(en)2]Br2 and NH4BCS. Moreover, a new "catalysis-crystal induction" mechanism in the preparation of the chiral Co(III) complex is put forward.国家自然科学基金(20171037,20373056);; 福建省自然科学基金(C0020001)资助项

Kinetic Investigation on the Mechanism of the Reduction of Imidazole Cobalt(Ⅲ) Complexes

Kinetic studies on the electron transFer(ET) reaction of [Co(NH3)5(ImH)]3+/[Fe(CN)6]4- and trans-[Co(NH3)(en)2(ImH)]3+/[Fe(CN)6]4- have been carried out at various temperatures.The results indicated that these two ET reactions Followed the outersphere mechanism.At 25℃,I=0.50mol'L-1, the ion pair Formation constants Qip ofthe prectirsor complexes in the ET reactions are 2.6×102 and 4.9 × 1O2mol'L-1 ,and theelectron transFer rate constants kct are 2.1 ×10-4 and 5.2 ×10-5s-1 respectively.The activation enthalpy and the activation entropy of these two processes are 1.2×1O2,0.8 ×102kJ 'mol -1 and 5.1×102, 3.6 ×102J·mol-1 ·K-1 respectively.国家自然科学基

Kinetic Investigation of the Ruduction For Crowded[Co(tmen)3]3+by[Fe(CN)6]4-

［fE（Cn）_6］--（4-）还原高位阻［CO（TMEn）_3］--（3＋）的反应动力学研究颜文斌，周朝晖，章慧，唐星原，徐志固（厦门大学化学系，厦门，361005）关键词电子转移反应，外配位界机理，三氯三（四甲基乙二胺）合钴（Ⅲ）ludI等［1，2］曾用...Kinetic studies of the outer-sphere electron transFer reaction between[Co(tmen)3]3+ and[Fe(CN)6]4- have been carried out at various temperatures and pH values.The ion-pair Formation constant Qip of the precursor complex[Co(tmen )3]3+[Fe(CN)6]4-is 5.6×102L·mol-1, and the rate constant ket For the electron transFer within the ion-pair is 6.8×10-3 s-1 at 25℃ and I=0.10 mol/L.The activation enthalpy and the activation entropy of this reaction are 1.6×102 kJ/mol and 6.5×102J/mol·K respectively.The mechanism of the reaction is discussed.国家自然科学基

Kinetic Investigation of Electron TransFer Reaction between trans - [(en)_2(NO_2)Co(O_2CC_5H_5N)]--(2+)/Fe（Ⅱ）

合成了新型CO(Ⅲ)配合物TrAnS-[(En)_2(nO_2)CO(O_2CC_5H_5n)](ClO_4)_2,并通过紫外可见光谱、红外光谱、元素分析和X射线单晶衍射分析进行了表征.同时分别以[fE(Cn)_6]--(4-)和[fE(Cn)_5(H_2O)]--(3-)作为还原剂,考察了该配合物被还原的反应动力学行为.结果表明两反应体系分别按外配位界机理和内配位界机理进行电子传递.在25℃,I=0.5MOl·l--(-1),TrAnS-[(En)_2(nO_2)CO(O_2CC_5H_5n)]--(2+)/[fE(Cn)_6]--(4-)反应体系的前驱配合物离子对形成常数Q_(IP)=29MOl--(-1)·l,电子转移速率常数k_(ET)=2.4x10--(-4)S--(-1),电子转移过程的活化焓△H_(ET)--≠和活化熵△S_(ET)--≠分别为1.2x10--2kJ·MOl--(-1)和5.0x10--2J·MOl--(-1)·k--(-1)在40℃,PH=8.0,I=0.1MOl·l--(-1),TrAnS-[(En)_2(nO_2)CO(O_2CC_5H_4n)]--(2+)/[fE(Cn)_5(H_2O)]--(3-)反应体系前驱双核配合物分子内电子转移速率常数为7.0x10--(-5)S--(-1).最后讨论了分子轨道对称性,两金属中心氧化还原电势差等因素对电子转移速率的影响.trans - [(en)2(NO2)Co(O2CC5H5N) ]2+ (C1O4)2, which is First reported, has been synthesized and characterized by elemental analysis, UV - Vis and IR spectra, and X - ray structural analyses.Kinetic behaviours of the Co( III) complex reduced by [Fe(CN)6]4- and [Fe (CN)5 (H2O)]3- have been investigated.The results indicated the electron transFer (ET) reactions Followed the outer- sphere mechanism or the inner- sphere mechanism respectively.At25℃ ,I= 0.50mol L-1, the ion - pair Formation constant Qip and ET rate constant ket of theprecursor complex For trans - [ (en)2 ( NO2 ) Co( O2CC5H5N) ]2+ /[ Fe(CN)6 ]4- are 29mol-1·Land 2.4 × 10-1s-1, the activation enthalpy △H≠er and the activation entropy △S≠er of this ETprocess are 1.2 × 102kJ·mol-1 and 5.0 ×102kJ·mol-1·K-1 respectively.The intramolecular ET rate constant of the precursor binuclear complex For trans - [(en)2(NO2)Co(O2CC5H4N) ] + /[Fe(CN)5(H2O)]3- is 7.0×10-5 at 40℃ , pH=8.0 and I= -0.10mol L-1.Finally the inFluence of the moar orbital symmetry and the redox potentials on ET rate have been discussed.国家自然科学基金资助的项

KINETIC INVESTIGATION OF THE REDUCTION FOR CROWDED [CO(TMEN)(3)](3+) BY [FE(CN)(6)](4-)

Kinetic studies of the outer-sphere electron transfer reaction between [Co(tmen)(3)](3+) and [Fe(CN)(6)](4-) have been carried out at various temperatures and pH values. The ion-pair formation constant Q(ip) of the precursor complex [Co(tmen)(3)](3+)- [Fe(CN)(6)](4-) is 5.6 X 10(2) L . mol(-1) and the rate constant k(et) for the electron transfer within the ion-pair is 6.8 X 10(-3) s(-1) at 25 degrees C and I= 0.10 mol/L. The activation enthalpy Delta H-et(not equal) and the activation entropy Delta H(et)not equal of this reaction are 1.6 X 10(2) kJ/mol and 6.5 X 10(2) J/mol . K respectively. The mechanism of the reaction is discussed

Kinetic investigation of electron transfer reaction between trans- (en)(2)(NO2)Co(O2CC5H5N) (2+)/Fe(II)

trans - [(en)(2)(NO2)Co(O2CC5H5N)](2+) (ClO4)(2), which is first reported, has been synthesized and characterized by elemental analysis, UV - Vis and IR spectra, and X - ray structural analyses. Kinetic behaviours of the Co(III) complex reduced by [Fe(CN)(6)](4-) and [Fe(CN)(5)(H2O)](3-) have been investigated. The results indicated the electron transfer (ET) reactions followed the outer-sphere mechanism or the inner-sphere mechanism respectively. At 25 degrees C, I = 0.50mol . L(-1), the ion-pair formation constant Q(ip) and ET rate constant k(et) of the precursor complex for trans - [(en)(2)(NO2)Co(O2CC5H5N)](2+)/[Fe(CN)(6)](4-) are 29mol(-1). L and 2.4 x 10(-1) s(-1), the activation enthalpy Delta H-et(not equal) and the activation entropy Delta S-et(not equal) of this ET process are 1.2 x 10(2)kJ . mol(-1) and 5.0 x 10(2)kJ . mol(-1). K-1 respectively. The intramolecular ET rate constant of the precursor binuclear complex for trans - [(en)(2)(NO2)Co(O2CC5H4N)](+)/[Fe(CN)(5)(H2O)](3-) is 7.0 x 10(-5) s(-1) at 40 degrees C, pH = 8.0 and I = -0.10mol . L(-1). Finally the influence of the molecular orbital symmetry and the redox potentials on ET rate have been discussed