CYANINE BORATE SALTS THAT FORM PENETRATED ION-PAIRS IN BENZENE SOLUTION - SYNTHESIS, PROPERTIES, AND STRUCTURE

A series of cyanine borate salts were prepared and studied by laser spectroscopy, fluorescence spectroscopy, NMR spectral methods, and computer modeling. Analysis of the chemical, physical, and spectral properties of these salts shows that, in benzene solution, they form penetrated ion pairs. The center-to-center distance between the ions is less than the sum of the individual ionic radii. We call such structures penetrated ion pairs. Penetration affects the properties of the cyanine dyes in unique ways that are described.