Unique reflection properties of thin films of organic soluble naphthalocyanines

Abstract

The reflection properties of a series of organic-soluble naphthalocyanines (Y₂MNcX₄1 and MNcX₄ 2), in thin films have been studied: their reflection properties were quite different. The maximal reflectivity of a thin film of an example of naphthalocyanine 1 such as (Et₃SiO)₂SiNc(SC₁₀H₂₁)₄(1b) was over 0.5 around the near IR region, whereas an example of compound 2 such as NiNc(Bu^t)₄(2a) showed broad reflection spectra below a reflectivity of 0.25 as a thin film. To explain these different reflection properties of thin films of 1 and 2, their complex dielectric constants (relative permittivities) determined from their experimentally obtained spectral data were analysed. The highly ordered J-type molecular arrangement of a thin film of 1 generated a sharp dielectric maximum with a large oscillator strength and a narrow peak width, whereas the complex and disordered molecular aggregation of a thin film of 2 induced a broad dielectric maximum. The unique differences between thin films of 1 and 2 arose from their dielectric properties.