Configuration of Charge Waves in Polymethine Linear Dye Systems

摘要

In the middle of the essential particular properties of linear conjugate systems 1, it is an ability to exhibit quasimetallic conductivity. The basis polymers 1 looks like [R-(CH)_m-R]~n, where n= 0, ±1, ±2. This discovery, awarded with the Nobel Prize in 2000, led to the revision of many theoretical models based on representations of the action of n -electrons in the conjugated molecules, primarily in anions and cations of polymethine dyes, in cation or anion radicals of polyenes, and thus inspired the improvement of original theoretical model of the electronic structure of similar special type of systems, taking into account the features of charge distribution and molecular geometry [1-4]. In addition to the use of conjugated systems as molecular conductors [1], they find numerous applications in nonlinear optics: as a result, polymethine dyes with uneven number of carbon group CH (system 1, where m= 2k+1,n= ±1, and R-various heterocyclic residues) are capable to intensively absorb and emanate a quant of light in visible part of spectrum and near-infrared part of the spectrum [5, 6]. Such unique spectral properties are suitable to the definite charge distribution in a main and in the excited state, as well as an arrangement of the lengths of carbon-carbon bonds [1-8]. According to modern notions, the carbon atom in the conjugate system is in the sp~3-hybridized state and accordingly, forms three a-bonds, resulting in the molecules 1 being flat, as can be seen in Fig. 1, which shows an example of polymethine ion at 5, n= + 1, R= CH_2. The last 2p_z-electron together with the same electrons of other carbon atoms forms a common collective n-electron system. The transition from a neutral conjugate molecule to ions that is the injection of an electron or a hole into a high polarizable common collective n-electronic system is accompanied by the manifestation of supposed soliton level (level of impurity) in the energy gap in addition to significant shift in both the c