Semi-experimental gas-phase structures of anthracene and rubrene (5,6,11,12-tetraphenyltetracene) were determined by means of gas electron diffraction (GED). The use of the flexible restraints in the refinement of the GED data successfully resolves non-equivalent C–C bond lengths. The tetracene core of an isolated rubrene molecule was found to exhibit a twist distortion of about 18°; this is less than DFT calculations predict (30–40°). The modified Feller–Peterson–Dixon method in conjunction with high-level DLPNO-CCSD(T) calculations was employed to resolve the discrepancy between the available experimental gas-phase enthalpies of formation for rubrene. The theoretical value of meets its recent experimental counterpart (765.6 ± 8.4 kJ mol⁻¹) and is in strong disagreement with the previous estimation (882 kJ mol⁻¹).

中文翻译：

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蒽和红荧烯的气相平衡分子结构和从头算热化学

通过气体电子衍射 (GED) 确定了蒽和红荧烯（5,6,11,12-四苯基并四苯）的半实验气相结构。在 GED 数据的改进中使用灵活的限制成功地解决了非等效的 C-C 键长。发现分离的红荧烯分子的并四苯核表现出约 18° 的扭曲变形；这小于 DFT 计算预测的 (30–40°)。采用改进的 Feller-Peterson-Dixon 方法结合高级 DLPNO-CCSD(T) 计算来解决红荧烯的可用实验气相生成焓之间的差异。的理论值符合其最近的实验对应物 (765.6 ± 8.4 kJ mol ^{-1) 并且与先前的估计 (882 kJ mol -1} )存在强烈分歧。