1H and 2-D NMR spectra of 1, 1'-diethyl-2, 2'-cyanine iodide in water and methanol

ORGN 564

Irina A. Struganova, istruganova@mail.barry.edu1, Tony Wallner, twallner@mail.barry.edu1, James Kelly, KellyJJ@buckmail.barry.edu1, and Ileana Pazos, pazosi@bucmail.barry.edu2. (1) Department of Physical Sciences, Barry University, 11300 NE 2nd Avenue, Miami Shores, FL 33161, (2) Department of Chemistry, Barry University, 11300 NE 2nd Ave, Miami Shores, FL 33161
1, 1'-Diethyl-2, 2'-Cyanine Iodide (PIC) is a well-studied and commercially available cyanine dye. PIC was the subject of numerous investigations due to its ability to form special molecular aggregates (J-aggregates) characterized by many unique optical properties. This ability, as well as unique optical properties of PIC J-aggregates, must be related to the molecular structure of the dye and/or electronic density distribution. Both structure and electronic density of molecules are reflected in the NMR spectra. Simple 1H-NMR spectrum of PIC is well known and signals from all protons, including the aromatic region, were assigned a long time ago. However, strangely enough, it seems that nobody attempted to investigate the PIC with 2-D proton NMR spectroscopy. We measured 2D COSY, dqCOSY and NOESY spectra of PIC in deuterated methanol and water. 2D NMR measurements revealed that a previously suggested assignment of protons in 1H-NMR spectra of PIC was not correct and suggested the re-assignment. Possible explanations of the differences in the proton NMR spectra of PIC in methanol and water are discussed.