Variable Conformation of Benzophenone in a Series of Resorcinarene-Based Supramolecular Frameworks

Ten supramolecular complexes incorporating benzophenone (BZP) as a guest have been synthesized
by hydrothermal and conventional methods and characterized by X-ray diffraction. They are CMCR·3bipy·2H2O·BZP (CMCR = C-methylcalix[4]resorcinarene; bipy = 4,4‘-bipyridine) 1, CMCR·bipy·BZP·H2O 2, CMCR·2bpe·BZP
(bpe = trans-1,4-bis(pyridyl)ethylene) 3, CMCR·2bpmh·BZP (bpmh = bis-(1-pyridin-4-yl-methylidene)-hydrazine)
4, CMCR·2bpeh·BZP·ethanol (bpeh = bis-(1-pyridin-4-yl-ethylidene)-hydrazine) 5, CMCR·2bipy·BZP 6, CECR·2bipy·BZP·0.5bipy (CECR = C-ethylcalix[4]resorcinarene) 7, CECR·2bpe·0.5BZP·0.5ethanol 8, CMCR·2bix·2BZP (bix =
1,4-bis(imidazol-1yl-methyl)benzene) 9, and CECR·2bix·2BZP 10. The resorcinarene molecule adopts a chair
conformation in 1, giving rise to a 3D stepped network. Compounds 2 and 3 have a brick-wall structure with boat-shaped CMCR but different spacer connectivity. A 3D 3-fold interpenetrating network exists in compound 4, whereas
a wavelike framework is found in 5. Crystals of 6, 7, and 8 contain carcerand-like capsules. The use of a more rigid
spacer generates 9 and 10, which exhibit a double buckled framework with large channels. The 10 phases contain
12 independent benzophenone molecules (9 and 10 each having two independent benzophenone molecules), eight of
which are fully ordered within the supramolecular framework. Benzophenone occurs as a monomer in 1, 5, 8 and
as a dimer in 2, 3, 4, 6, and 7, while polymeric aggregates are found in 9 and 10. The dihedral angles between the
two phenyl rings of benzophenone vary from 42.0 to 67.9°, and correlate with the central C−C−C bond angles,
which decrease with increasing dihedral angle. Quantum-mechanical calculations indicate the energy of the distortion
imposed by the framework to range up to 32 kJ/mol, which is significant relative to the ∼85 kJ/mol lattice energy
of the known neat benzophenone phases.

本研究通过水热法与常规合成策略，制备了10种以二苯甲酮（benzophenone, BZP）为客体的超分子配合物，并通过X射线衍射完成结构表征。具体化合物如下：CMCR·3bipy·2H₂O·BZP（CMCR = 对甲基杯[4]间苯二酚芳烃（C-methylcalix[4]resorcinarene）；bipy = 4,4'-联吡啶（4,4‘-bipyridine））1、CMCR·bipy·BZP·H₂O 2、CMCR·2bpe·BZP（bpe = 反式-1,4-二(吡啶基)乙烯（trans-1,4-bis(pyridyl)ethylene)）3、CMCR·2bpmh·BZP（bpmh = 双(1-吡啶-4-基亚甲基)肼（bis-(1-pyridin-4-yl-methylidene)-hydrazine））4、CMCR·2bpeh·BZP·乙醇（bpeh = 双(1-吡啶-4-基亚乙基)肼（bis-(1-pyridin-4-yl-ethylidene)-hydrazine））5、CMCR·2bipy·BZP 6、CECR·2bipy·BZP·0.5bipy（CECR = 对乙基杯[4]间苯二酚芳烃（C-ethylcalix[4]resorcinarene））7、CECR·2bpe·0.5BZP·0.5乙醇 8、CMCR·2bix·2BZP（bix = 1,4-二(咪唑-1-基甲基)苯（1,4-bis(imidazol-1yl-methyl)benzene））9以及CECR·2bix·2BZP 10。在化合物1中，间苯二酚芳烃分子采取椅式构象，由此形成三维阶梯状网络结构。化合物2与3均以船型构象的CMCR为骨架，拥有砖墙式结构，但二者的连接基连接方式存在差异。化合物4呈现三维三重互穿网络结构，而化合物5则为波浪状骨架。化合物6、7和8的晶体结构中存在类穴状胶囊结构。采用刚性连接基合成的化合物9与10，展现出带有大孔道的双褶皱骨架结构。该10个配合物相中共包含12个独立的二苯甲酮分子（化合物9和10各含2个独立的二苯甲酮分子），其中8个二苯甲酮分子在超分子骨架中完全有序排列。二苯甲酮在化合物1、5、8中以单体形式存在，在化合物2、3、4、6、7中以二聚体形式存在，而在化合物9和10中则以聚合物聚集体形式存在。二苯甲酮两个苯环之间的二面角介于42.0°至67.9°之间，且与中心C−C−C键角存在相关性：随着二面角增大，中心键角逐渐减小。量子力学计算结果表明，骨架诱导产生的畸变能最高可达32 kJ/mol，相较于已知纯二苯甲酮相约85 kJ/mol的晶格能，该畸变能具有显著影响。