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测量了2-烷基TCNQ(C8TCNQ,C12TCNQ,C18TCNQ)浇铸膜的红外光谱,发现这类化合物的红外CH2剪式振动在1 471和1 462 cm-1处显示2个峰。这2个峰的强度比(I1 471/I1 462)随着烷基链的长度增加而明显减少。另外,来自CH2的1 471 cm-1吸收峰与来自TCNQ环的1 529 cm-1吸收峰的相对强度随着碳链的长度增加而不发生变化。CnTCNQ系列化合物的红外光谱CH2的剪式振动行为与长链脂肪酸中CH2行为很不相同。在长链脂肪酸中,晶体场效应导致了剪式振动分裂。考虑C12TCNQ的晶体结构,而将1 471cm-1峰归属为非叉指对接的碳链,将1 462 cm-1峰归于叉指对接的碳链,双峰的出现与晶体场分裂无关。并且得到烷基TCNQ中,非叉指对接的碳链的长度与碳链总长度无关的结论。
The infrared spectra of 2-alkyl TCNQ (C8TCNQ, C12TCNQ, C18TCNQ) films were measured and found that the infrared CH2-scission vibration of these compounds showed two peaks at 1 471 and 1 462 cm-1. The intensity ratio (I1 471 / I1 462) of these two peaks is significantly reduced as the length of the alkyl chain increases. In addition, the relative intensity of the 1 471 cm-1 absorption peak from CH2 and the 1 529 cm-1 absorption peak from the TCNQ ring did not change as the carbon chain length increased. The infrared spectra of CnTCNQ series compounds show that the scissoring vibration behavior of CH2 is very different from the CH2 behavior of long chain fatty acids. In long-chain fatty acids, the crystal field effect causes scissor-type vibrational fragmentation. Considering the crystal structure of C12TCNQ, the 1 471 cm-1 peak is attributed to the non-interdigitated carbon chain, and the 1 462 cm-1 peak is attributed to the interdigitated carbon chain. The appearance of bimodal has nothing to do with the splitting of the crystal field. And the conclusion is obtained that the length of the carbon chain which is not interdigitated in the alkyl TCNQ has nothing to do with the total length of the carbon chain.