Structure–Property Relationships of Dibenzylidenecyclohexanones

A series of symmetrical
dibenzylidene derivatives of cyclohexanone
were synthesized with the goal of studying the physicochemical properties
of cross-conjugated dienones (ketocyanine dyes). The structures of
the products were established and studied by X-ray diffraction, NMR
spectroscopy, and electronic spectroscopy. All products had the E,E-geometry. The oxidation and reduction
potentials of the dienones were determined by cyclic voltammetry.
The potentials were shown to depend on the nature, position, and number
of substituents in the benzene rings. A linear correlation was found
between the difference of the electrochemical oxidation and reduction
potentials and the energy of the long-wavelength absorption maximum.
This correlation can be employed to analyze the properties of other
compounds of this type. The frontier orbital energies and the vertical
absorption and emission transitions were calculated using quantum
chemistry. The results are in good agreement with experimental redox
potentials and spectroscopic data.

本研究合成了一系列对称的环己酮二亚苄基衍生物，旨在探究交叉共轭二烯酮（cross-conjugated dienones）的理化性质，该类化合物亦被称为酮花青染料（ketocyanine dyes）。通过X射线衍射（X-ray diffraction）、核磁共振波谱（NMR spectroscopy）与电子光谱学（electronic spectroscopy），对产物的结构进行了确证与表征。所有产物均具有E,E-构型（E,E-geometry）。采用循环伏安法（cyclic voltammetry）测定了该类二烯酮的氧化还原电位，研究表明该电位取决于苯环上取代基的种类、位置与数目。研究发现，电化学氧化与还原电位之差与长波长吸收峰的最大能量之间存在良好的线性相关关系，该相关性可用于分析该类其他化合物的相关性质。采用量子化学（quantum chemistry）方法计算了该类化合物的前线轨道能（frontier orbital energies）与垂直吸收及发射跃迁（vertical absorption and emission transitions），计算结果与实验测得的氧化还原电位及光谱数据吻合良好。