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首页> 外文期刊>Journal of structural chemistry >Infrared spectra of diphenylphthalide and polydiphenylenephthalide
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Infrared spectra of diphenylphthalide and polydiphenylenephthalide

机译：联苯二苯和聚苯二苯的红外光谱

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The splitting of the ν(C=O) absorption band (AB) of about 12 cm~(?1) is found in the IR spectra of diphenylphthalide (DPP) in the crystalline phase and CCl_4 solution. In the crystalline phase, this splitting is likely to be caused by the inequivalence of DPP molecules in the crystallographic cell, while in the solution, by the dimerization of DPP molecules via dipole-dipole and/or hydrogen bonds. A theoretical low-frequency shift of the ν(C=O) AB for a complex of two DPP molecules (in comparison with a single molecule) is 14 cm~(?1) in the PBE/3ξ approximation, which is close to the experimentally observed splitting. In two quantum chemical approximations (B3LYP/6-311G(d,p) (I) and PBE/3ξ (II)) the optimal structure and vibrational spectrum of DPP are calculated. Approximation I better reproduces the intensities, whereas approximation II better reproduces the IR frequencies of the DPP spectrum. Almost all 48 ABs of the IR spectrum of DPP are assigned to theoretical normal vibrations (modes). Based on the potential energy distribution over natural coordinates and the visualization of vibrations, experimental ABs (and the corresponding modes) are assigned to the stretching and bending vibrations of certain bonds in the DPP molecule. In particular, ABs at 1107 cm~(?1) and 970 cm~(?1) are assigned to the ν(-OC-O-) and ν(-C-O-) stretching vibrations, respectively, of the DPP lactonic ring, which differs from the previously accepted assignment. The results of the interpretation of the DPP spectrum are used to assign a number of ABs in the IR spectrum of polydiphenylenephthalide (PDP), for which DPP is a model compound. According to the calculations in approximation II of the vibrational spectrum of a model valence-bonded dimeric molecule, the intense complex AB at 800-870 cm~(?1) in the IR spectrum of PDP is mainly due to the out-of-plane bending vibrations of C-H bonds in the 1,4-substituted benzene rings of polymer biphenyl moieties and the bending vibrations of the lactonic ring.
机译：在结晶相和CCl_4溶液中的二苯基邻苯二甲酸酯（DPP）的红外光谱中发现约12 cm〜（？1）的ν（C = O）吸收带（AB）分裂。在结晶相中，这种分裂很可能是由于晶体学单元中DPP分子的不等性引起的，而在溶液中，是通过DPP分子通过偶极-偶极和/或氢键的二聚作用引起的。在PBE /3ξ近似中，两个DPP分子（与单个分子相比）的复合物的ν（C = O）AB的理论低频位移为14 cm〜（？1）。实验观察到的分裂。在两个量子化学近似中（B3LYP / 6-311G（d，p）（I）和PBE /3ξ（II）），计算了DPP的最佳结构和振动光谱。近似值I更好地再现了强度，而近似值II更好地再现了DPP光谱的IR频率。 DPP的IR光谱中几乎所有48个AB都分配了理论上的正常振动（模式）。基于自然坐标上的势能分布和振动的可视化，将实验性AB（以及相应的模式）分配给DPP分子中某些键的拉伸和弯曲振动。特别是，将1107 cm〜（？1）和970 cm〜（？1）处的AB分别分配给DPP内酯环的ν（-OC-O-）和ν（-CO-）拉伸振动，与先前接受的分配不同。 DPP光谱的解释结果用于指定聚对二苯二甲酰苯（PDP）的IR光谱中的多个AB，DPP是模型化合物。根据模型价键二聚体分子振动光谱的近似式II计算，PDP红外光谱中800-870 cm〜（？1）处的强络合物AB主要是由于面外聚合物联苯部分的1,4-取代苯环中CH键的弯曲振动和内酯环的弯曲振动。

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