9,10-Anthraquinones Disubstituted with Linear Alkoxy Groups: Spectroscopy, Electrochemistry, and Peculiarities of Their 2D and 3D Supramolecular Organizations

Abstract

Spectroscopic, electrochemical, and structural properties of 2,6-dialkoxy-9,10-anthraquinones (Anth-OCn, n = 4, 6, 8, 10, and 12) of increasing alkoxy substituents length were investigated. UV–vis spectroscopy showed a substitution-induced bathochromic shift of the least energetic band from 325 nm in the case of unsubstituted anthraquinone to ca. 350 nm for the studied derivatives. Similarly as unsubstituted anthraquinone, the studied compound showed two reversible one electron reductions to a radical anion and spinless anions, respectively. The first reduction was affected by electron-donating properties of the substituents, its potential being shifted to ca. −1.5 V (vs Fc/Fc+), i.e., by 80 to 95 mV as compared to the case of unsubstituted anthraquinone. This corresponded to a decrease of |EA| from 3.27 to 3.19–3.17 eV. The experimental spectroscopic and electrochemical data were in full agreement with the DFT calculations. The introduction of the alkoxy substituent improved solution processibility of the studied compounds and facilitated the formation of their ordered supramolecular 2D aggregation on HOPG as well as single crystal growth from solutions. Comparative structural investigations carried out on single crystals and monolayers deposited on HOPG revealed two, mutually related, effects of the substituent length on the resulting supramolecular organization. The first one concerns both the 2D organization in the monolayers and 3D molecular arrangement in crystals: increasing substituent length evolution of the structure occurs from herringbone-type to lamellar. The second effect, observed in monolayers of the derivatives with longer substituents, concerns gradual evolution of their lamellar structures with increasing substituent length. This evolution is induced by the structure of the graphite substrate and involves increasing correlation of the molecules orientation (anthraquinone cores as well as alkoxy substituents) with the symmetry of the graphite substrate. As a result, their 2D and 3D structures become dissimilar.

New luminescent organoboron esters based on damnacanthal: one-pot multicomponent synthesis, optical behavior, cytotoxicity, and selectivity studies against MDA-MBA-231 breast cancer cells

“…All compounds present two absorption peaks in the UV region (351 nm and B267 nm) and a shoulder in the visible region (B426 nm). The low energy peaks with a small extinction coefficient are ascribed to the np* transition of fused aromatic rings and quinone backbones as previously reported, 31 while the highest energy peaks are assigned to electronic transition from the underlying occupied molecular orbitals to the LUMO. The calculated optical band gap (Eg Opt ) for each compound classifies these materials as semiconductors (Table 2).…”

Thermodynamics of self-assembled molecular layers of trimesic acid from fields-supported kinetic Monte Carlo simulation

“…[1][2][3][4] The surface-confined self-assembly usually leads to the formation of supramolecular structures, which is hardly possible in the bulk phase. This is applied in functional organic films used, for example, in organic electronics [5][6][7][8][9][10] and catalysis. 3,[11][12][13] An equilibrium structure of the film is determined by a delicate balance between the energy gained and entropy lost upon molecular adsorption and association.…”

Thermodynamics of Rigid Self-Assembled Crystals: Molecular Simulation of Two-Phase Systems under External Fields

“…The self-assembly of functional organic molecules on solid surfaces is a vivid example of the molecular self-assembly into supramolecular structures having various engineering applications such as organic electronics, − sensors, ,,− catalysis, − etc. On the current level of organic synthesis, it is possible to obtain functional molecules with any possible structure and properties.…”