Crystalline structure of two-dimensional cyanine dye J-aggregates

A crystallographic analysis of optical fluorescent images of two-dimensional polygonal structures of J-aggregates of 3,3′-di(γ-sulfopropyl)-5,5′-dichlorothiamonomethinecyanine (MCD) cyanine dye has been performed. In aqueous solutions, MCD forms striplike J-aggregates in the form of extended strips with parallel sides and an oblique or right-angled end. It is found that the acute angle in oblique J-aggregates has a single value close to 45°. The staircase model of molecular packing in oblique J-aggregates is proposed with a slippage angle of 25° expected from the molecular simulation. Within this model the sides of aggregates are formed by the [100] and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$[\bar 110]$$\end{document} faces, and the acute angle between them is equal to the experimentally observed angle. Right-angled rectangular J-aggregates are presumably described by the ladder model.