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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Synthesis, Photochemistry, and Electrochemistry of a Series of Phthalocyanines with Graded Steric Hindrance
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Synthesis, Photochemistry, and Electrochemistry of a Series of Phthalocyanines with Graded Steric Hindrance

机译：一系列具有梯度立体阻滞作用的酞菁类化合物的合成，光化学和电化学

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摘要

A group of twelve new and three known silicon phthalocyanines having axial ligands and peripheral groups which provide varying amounts of steric protection to the ring face and ring periphery has been assembled. These are SiPc[OSi(n-C_6H_(13))_3]_2, 1, (known), SiPc[OSi(i-C_4H_9)_2(n-C_(18)H_(37))]_2, 2, SiPc(OEt)_8[OH]_2, 5, SiPc(OEt)_8[OSi(CH_3)_3]_2, 6, SiPc(OnBu)_8[OH]_2, 8, (known), SiPc(OnBu)_8[OSi(n-C_6H_(13))_3]_2, 9, (known), SiPc(OnBu)_8[OSi(i-C_4H_9)_2(n-C_(18)H_(37))]_2, 10, SiPc(dib)_4(OnBu)_8[OH]_2, 15, SiPc(dib)_4(OnBu)_8[F]_2, 16, SiPc(dib)_4(OnBu)_8[OSi(n-C_6H_(13)_2]_2, 17, SiPc(dib)_4(OnBu)_8[OSi(i-C_4H_9)_2(n-C_(18)H_(37)]_2, 18, SiPc(dib)_4(OnBu)_8[OSi_8O_(12)(C_5H_9)_7]_2, 19, SiPc(dib)_4(OnBu)_8[OH]_2, 22, SiPc(dib)_4(OiBu)_8[OSi(n-C_6H_(13))_3]_2, 23, and SiPc(dib)_4(OiBu)_8[OSi_8O_(12)(C_5H_9)_7]_2, 24. Syntheses are given for the twelve members of the group that are new. Photophysical and voltammetric investigations of six representative members of the group, 1, 2, 10, 18, 19, and 24, have been carried out. The results show that compounds 1 and 2 (no butoxy substituents at the 1 and 4 positions) have significantly larger values of the first oxidation potential (E_(+1)) than those compounds (10, 18, 19, and 24) that do carry these substituents. The values of E_(-1) (first reduction potential) show very little in the way of structural dependence. Alkoxy substitution at the 1,4 positions affects the HOMO energies, and therefore, the addition of an electron from an electrode to the LUMO of a 1,4 substituted silicon phthalocyanine will not be a sensitive function of the substitution pattern. The removal of an electron from the HOMO in an oxidation step on the other would be expected to be energetically less demanding for those compounds wherein the HOMO is higher lying. This orbital energy effect of substitution makes it clear why the E_(+1) values for compounds 1 and 2 are significantly lower. Substitution of dibenzobarreleno (dib) at the 2,3 positions has only minor effects on the HOMO energy, as shown by the similarities in the position of the Q-band maximum. However, it is very likely that the steric effects of the dibenzobarreleno substituents and the [OSi_8O_(12)(C_5H_9)_7] axial cages contribute to the observed trends in E_(+1). Bimolecular rate constants for quenching of the triplet states of the six target compounds by O_2, by β-carotene, and by chloranil were measured. The first two compounds quench by triplet-triplet (TT) energy transfer, whereas the last is an electron transfer (ET) reactant. All rate parameters were sensitive to the steric crowding of the phthalocyanine π system, but with different degrees. The least sensitive was the ET reaction with chloranil. Thus, it appears that although steric crowding of the triplet state of the silicon phthalocyanines is very effective at reducing the rate constants of exoergic electron exchange energy transfer (TT) reactions, even for a small molecule such as oxygen, it is much less effective at discriminating against electron transfer (ET) processes. These differences may be accounted for on the concept that the overlap requirement for the double electron exchange of TT energy transfer is more stringent compared to the single electron transfer (ET).
机译：已经组装了一组十二种新的和三种已知的具有轴向配体和外围基团的硅酞菁，这些轴向配体和外围基团为环面和环外围提供不同量的空间保护。这些是SiPc [OSi（n-C_6H_（13））_ 3] _2，1，（已知），SiPc [OSi（i-C_4H_9）_2（n-C_（18）H_（37））] _ 2，2，SiPc （OEt）_8 [OH] _2，5，SiPc（OEt）_8 [OSi（CH_3）_3] _2，6，SiPc（OnBu）_8 [OH] _2，8，（已知），SiPc（OnBu）_8 [OSi （n-C_6H_（13））_ 3] _2，9 ,,（已知），SiPc（OnBu）_8 [OSi（i-C_4H_9）_2（n-C_（18）H_（37））] _ 2，10，SiPc（ dib）_4（OnBu）_8 [OH] _2，15，SiPc（dib）_4（OnBu）_8 [F] _2，16，SiPc（dib）_4（OnBu）_8 [OSi（n-C_6H_（13）_2] _2，17，SiPc（dib）_4（OnBu）_8 [OSi（i-C_4H_9）_2（n-C_（18）H_（37）] _ 2，18，SiPc（dib）_4（OnBu）_8 [OSi_8O_（12 ）（C_5H_9）_7] _2，19，SiPc（dib）_4（OnBu）_8 [OH] _2，22，SiPc（dib）_4（OiBu）_8 [OSi（n-C_6H_（13））_ 3] _2，23 ，以及SiPc（dib）_4（OiBu）_8 [OSi_8O_（12）（C_5H_9）_7] _2，24.对该组的十二个新成员进行了合成。该组六个代表性成员的光物理和伏安研究，1、2、10、18、19和24的结果表明，化合物1和2（在1和4位没有丁氧基取代基）的第一氧化电位（E_（ +1） ），而不是带有这些取代基的化合物（10、18、19和24）。 E _（-1）（第一个还原电位）的值在结构依赖性方面显示很少。 1,4位上的烷氧基取代会影响HOMO能量，因此，将电子从电极添加到1,4取代的硅酞菁的LUMO上不会成为取代模式的敏感功能。另一方面，在HOMO较高位置的那些化合物上，期望在氧化步骤中从HOMO中除去电子对能量的需求较低。取代的这种轨道能量效应清楚地说明了为什么化合物1和2的E _（+ 1）值明显更低。如在Q波段最大值位置的相似性所示，在2,3位上取代二苯并barreleno（dib）对HOMO能量的影响很小。但是，很可能二苯并桶螺取代基和[OSi_8O_（12）（C_5H_9）_7]轴向笼的空间效应有助于E _（+ 1）的观察趋势。测量了O_2，β-胡萝卜素和邻苯二甲酰氯淬灭六种目标化合物三态态的双分子速率常数。前两种化合物通过三重态-三重态（TT）能量转移猝灭，而最后一种是电子转移（ET）反应物。所有速率参数均对酞菁π系统的空间拥挤敏感，但程度不同。最不敏感的是与氯苯胺的ET反应。因此，看来尽管硅酞菁的三重态在空间上拥挤在降低放热电子交换能量转移（TT）反应的速率常数方面非常有效，即使对于小分子，例如氧气，其效果也要差得多。区分电子转移（ET）过程。这些差异可能是由于以下概念造成的：与单电子转移（ET）相比，TT能量转移的双电子交换的重叠要求更为严格。

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