IR spectra of photopolymerized C60 films. Experimental and density functional theory study.
IR spectra of photopolymerized C60 films. Experimental and density functional theory study.
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DOI：
10.1021/jp053867y
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发表时间：
2006-08
期刊：
影响因子：
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通讯作者：
S. Stepanian;V. Karachevtsev;A. M. Plokhotnichenko;L. Adamowicz;A. M. Rao
中科院分区：
文献类型：
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作者：
S. Stepanian;V. Karachevtsev;A. M. Plokhotnichenko;L. Adamowicz;A. M. Rao
在1500-450 cm ~（-1）范围内测量了同时沉积和紫外光照射所得光聚合富勒烯薄膜的红外光谱。C60膜的聚合度估计为约95%。为了帮助指定的薄膜的实验红外光谱，量子化学计算的C60二聚体和三聚体的平衡结构进行了DFT（B3 LYP）/3- 21 G水平的理论。接下来，计算这些结构的IR频率和强度。对于计算中发现的五-三聚体结构，在B3 LYP/4- 31 G和B3 LYP/6- 31 G水平下确定相对稳定性，并用于选择能量最低的三聚体，即三聚体A（单体中心之间的角度为90度）和三聚体B（单体中心之间的角度为120度）。接下来，将聚合的富勒烯膜的IR光谱与最低能量的二聚体和两个最低能量的三聚体的计算频率进行比较。在此分析的基础上，并在比较的薄膜光谱与红外光谱的C60的二聚体和三聚体光谱通过其他方法获得，它表明，薄膜的主要成分是C60二聚体和正交（O）聚合物相。虽然在大多数情况下，不同的C60相的振动频率是相似的，我们发现了一些独特的光谱特征的C60二聚体和其他聚合物，可以用来确定聚合的C60膜的组成。
IR spectra of photopolymerized fullerene films obtained by simultaneous deposition and UV irradiation were measured in the range of 1500-450 cm(-1). The degree of the polymerization of the C60 films was estimated to be about 95%. To assist the assignment of the experimental IR spectra of the films, quantum chemical calculations of the equilibrium structures of the C60 dimers and trimers were performed at the DFT(B3LYP)/3-21G level of theory. Next, IR frequencies and intensities for those structures were calculated. For the five-trimer structures found in the calculations, the relative stabilities were determined at the B3LYP/4-31G and B3LYP/6-31G levels and used to select the lowest-energy trimers, which are Trimer A (angle between monomer centers is 90 degrees ) and Trimer B (angle between monomer centers is 120 degrees). Next, the IR spectra of the polymerized fullerene films were compared with the calculated frequencies of the lowest-energy dimer and the two lowest-energy trimers. On the basis of this analysis and on the comparison of the film spectra with the IR spectra of the C60 dimer and trimer spectra obtained by other methods, it was shown that the main components of the films are C60 dimers and the orthorhombic (O) polymer phase. The tetragonal (T) and rhombohedral (R) polymers, as well as small amounts of monomers, were also found. Although vibrational frequencies of different C60 phases are similar in most cases, we found several unique spectral features of the C60 dimer and other polymers that may be used to determine the composition of the polymerized C60 film.