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ABSTRACT:In this work, we present theoretical evidence illustrating that cyano derivatives of conducting polymers such as polythiophene, polycyclopentadiene, and polyfulvene have smaller intrinsic band gaps than those of their parent polymers. The geometric and electronic properties of the parent and the derivative polymers were Ž . studied with the use of two methodologies: 1 the pseudo-one-dimensional bandstructure calculations performed using the semi-empirical molecular orbital theory Ž . Ž. MNDO, AM1 and 2 oligomer calculations performed using the ab initio molecular orbital theory both at the Hartree᎐Fock and configuration interaction levels. In particular, Ž . Ž . we found that an organic polymer, poly dicyanomethylene cyclopentadifulvene PCNFv , Ž . Ž has a comparable possibly lower band gap to the one observed in poly dicyanomethylene . Ž . Ž . cyclopentadithiophene PCNTH which has a band gap of 0.8 eV . The precursor of Ž . Ž . PCNFv is poly dicyanomethylene cyclopentadicyclopentadiene PCNCY in which two cyclopentadiene rings are connected by a dicyanomethylene group. The additional bond Ž . conjugation in contrast to PCNCY perpendicular to the chain axis makes PCNFv very rigid and fully planar. Trends in structural properties indicate that the lower band gaps in the cyano-substituted polymers, in comparison to their parent polymers, are accompanied by a decrease in bond alternations in the aromatic or trans᎐cisoid forms and by an increase in bond alternations in the quinoid or cis᎐transoid forms.

Interrogating cellular nano-architecture may help reveal previously unknown structure-function relations. The three-dimensional mass-density distribution plays an important role in quantifying cellular structure. For instance, chromatin structure can be directly represented by the mass-density, as the individual molecules have similar mass and larger density generally indicates higher level of compaction. Chromatin compaction, in turn, is associated with gene transcription and is crucial in various aspects of fundamental biology, genetics, and oncology studies [1]. Moreover, it has been reported that a statistical representation of mass-density distribution by autocorrelation function (ACF) is crucial in stratifying risk of cancer in early stages [2]. Recent developments such as Partial Wave Spectroscopy [3] have gained success in cancer diagnosis by detecting three-dimensional sub-diffraction chromatin mass-density ACF alterations between malignant cells and healthy cells for various types of cancers.