Diamagnetic Properties of Mixtures of Nematic Liquid Crystal with Chlorophylls and Carotenoids

Abstract
The magnetic susceptibility and diamagnetic anisotropy of the mixtures of nematic 5CB with chlorophyll a (Chl. a), chlorophyll b (Chl. b) and carotenoids, which were synthesized in the form of extracts, with different concentrations of components have been studied. The pigments were extracted from finely ground powder of air-dried biomass of the aquatic plant Ceratophyllum demersum L., grown from a laboratory culture. The probable configuration of the molecules of substances in a magnetic field was considered. Taking into account the orientational features of the liquid crystal 5CB, the expressions for the diamagnetic anisotropy of its mixtures with various extracts were derived. Using the Faraday method, with the direct measurement of the force acting on a mixture in a magnetic field, the dependences of longitudinal and transverse components of the magnetic susceptibility and diamagnetic anisotropy of the mixtures on temperature were obtained. The amplitude differences in the temperature dependences of diamagnetic anisotropy for various mixtures were analyzed. The influence of currents in benzene rings of the liquid crystal and in conjugated aromatic porphyrin macrocycles, as well as in aliphatic chains of organic molecules on diamagnetic anisotropy was estimated.

Keywords: nematic liquid crystal, magnetic susceptibility, diamagnetic anisotropy