Conjugated Chain Length Research Articles

Exploring the two-photon absorption response in short π-chain organic compounds: Hydrazones and pyrazolines derivatives

We compared the experimental two-photon absorption spectra of two hydrazone derivatives of chalcone (HDC-1 and HDC-2) and two pyrazoline derivatives of dibenzylideneacetone and chalcone (PD-1 and PD-2). The compounds were synthesized by the Claisen-Schmidt reaction and characterized using NMR, FTIR, and UV–Vis. Using femtosecond pulses, the Z-scan technique recorded two-photon absorption cross-section (σ2PA) spectra of the investigated compounds, which presented values of σ2PA, ranging from ∼12 GM to ∼50 GM. Such σ2PA difference is generally associated with the conjugated chain length and the different functional and peripherical groups used. For example, increasing the π-chain and peripherals donor groups p-OCH3 from HDC-1 to HCD-2 led to a change in the σ2PA magnitude (σHDC−12PA∼35GM, σHDC−22PA∼50GM). The modification on the pyrazoline derivatives, i.e., increasing the conjugated chain and adding p-OCH3 in both phenyls in the PD-2 compared to compound PD-1 doubled the σ2PA magnitude (σPD−12PA∼12GM, σPD−22PA∼22GM). According to the obtained results and considering the investigated compounds' short π-chain, we could claim that these classes of organic molecules promise nonlinear optical materials for optical limiting due to optical transparency ranging from 450 nm for pyrazolines to 550 nm for hydrazone derivatives.

Electrochromic conjugated polymers containing benzotriazole and thiophene performing sub-second response time and 916 cm2 C−1 superb coloration efficiency

In pursuit of high-performance electrochromic conjugated polymers (ECPs), three benzotriazole-thiophene ECPs employing benzotriazole as acceptor and different thiophene repeating units as donors, namely, PBTz-T, PBTz-BT, and PBTz-TT, were synthesized via direct (hetero)arylation polymerization (DHAP). Meanwhile, following the above ECPs model, we investigated the effect of corresponding conjugated chain length of monomers on their optical, electrochemical and electrochromic properties. The results showed that along with the increase of the numbers of thiophene in the repeating unit of ECPs, the electronic and optical band gaps decreased, the UV–Vis absorption and fluorescence spectra showed significant bathochromic shift, and the electrochemical cycle stability gradually improved. PBTz-T exhibited giant coloration efficiency (916 cm2 C−1 at 530 nm), which is one of the best results in the visible region. And higher coloration efficiency means less energy consumption, which holds great potential for various applications, including electrochromic back covers of smartphones. PBTz-BT displayed the highest transmittance (28% at 550 nm), and BTz-TT illustrated the fastest switching time (0.6 s/0.5 s for doping/dedoping process). Flexible electrochromic device (ECD) fabricated employed PBTz-T as functional layer gradually changed from red (reduction) to dark green (oxidation), and maintained good cycling stability.

Preparation, characterization and electrocatalytic performance of a novel poly(2,5-di(thienyl)pyrrole) modified electrode bearing TEMPO

A novel monomer 2,5-di(thienyl)pyrrole bearing TEMPO, 4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)benzoyl-oxy-2,2,6,6-tetramethylpiperidin-1-yloxy (SNS-TEMPO) was synthesized. The corresponding polymer modified electrode (PSNS-TEMPO) was successfully prepared by cyclic voltammetry, and characterized by SEM, EDS, XPS and element mapping. For comparison, another novel monomer 4-​(1H-​pyrrol-​1-​yl)​benzoyl-oxy-2,2,6,6-tetramethylpiperidin-1-yloxy (N-TEMPO) was synthesized and the corresponding polymer modified electrode (PN-TEMPO) was prepared. Introduction of thiophene unit on each side of pyrrole unit to extend the conjugation chain length was propitious to make the electropolymerization of SNS-TEMPO easier. In addition, the electrocatalytic performance for electrooxidative self-coupling of benzylamine to N-benzylidenebenzylamine on PSNS-TEMPO was better than that on PN-TEMPO prepared under similar conditions. The possible reaction mechanism of benzylamine self-oxidation coupling reaction with PSNS-TEMPO was proposed.

Energy Storage Application of Conducting Polymers Featuring Dual Acceptors: Exploring Conjugation and Flexible Chain Length Effects.

Solution-processable conducting polymers (CPs) are a compelling alternative to inorganic counterparts because of their potential for tuning chemical properties and creating flexible organic electronics. CPs, which typically comprise either only an electron donor (D) or its alternative combinations with an electron acceptor (A), exhibit charge transfer behavior between the units, resulting in an electrical conductivity suitable for utilization in electronic devices and for energy storage applications. However, the energy storage behavior of CPs with a sequence of electron acceptors (A-A), has rarely been investigated, despite their promising lower band gap and higher charge carrier mobility. Utilizing the aforesaid concept herein, four CPs featuring benzodithiophenedione (BDD), and diketopyrrolepyrrole (DPP) are synthesized. Among them, the BDDTH-DPPEH polymer exhibited the highest specific capacitance of 126.5 F g-1 at a current density of 0.5 A g-1 in an organic electrolyte over a wide potential window of -0.6-1.4V. Notably, the supercapacitor properties of the polymeric electrode materials improved with increasing conjugation length by adding thiophene donor units and shortening the alkyl chain lengths. Furthermore, a symmetric supercapacitor device fabricated using BDDTH-DPPEH exhibited a high-power density of 4000W kg-1 and an energy density of 31.66Wh kg-1 .

A post-synthetic modified NH2-MIL-125 (Ti) catalyst for boosting photochemical Cr (VI) reduction

MOFs-based composites with visible light response have gradually attracted wide researchers’ attention to water environmental remediation. Herein, a series of post-synthesis modified (PSM) NH2-MIL-125 (Ti) (R-BA-MIL-125 (Ti)) with phenyl-Schiff base-phenyl conjugate systems were successfully synthesized by a simple post-synthetic modification method. Under the optimization of catalyst structure designing, the photocatalytic reduction of Cr (VI) follows the order: –OH > -CH3 > -H > -Cl > -NO2-BA-MIL-125 (Ti) > NH2-MIL-125 (Ti). Among them, 4-hydroxybenzaldehyde-modified NH2-MIL-125 (Ti) (OH-BA-MIL-125 (Ti)) exhibited the highest photocatalytic removal efficiency of hexavalent chromium (Cr (VI)) at visible light conditions and the removal rate for Cr (VI) reached 98.3% under 90 min with only 5 mg photocatalyst, which displayed 2.07 times that of NH2-MIL-125 (Ti). The introduction of para-substituted benzaldehydes not only extended the conjugated chain length, but also subtly reduced the band-gap energy (Eg) of NH2-MIL-125 (Ti). Benefitting from broadening the range of photo-response and enhancing the ability of photoelectron generation, it could significantly enhance the ability of NH2-MIL-125 (Ti) to remove Cr (VI). ESR analyses indicate that e- and •O2- are the main active species. In addition, OH-BA-MIL-125 (Ti) exhibited good reusability and stability over 5 cycles. Therefore, this work will provide new insights into the fabrication of highly active catalysts by PSM for the remediation of chromium-containing wastewater.

Solvent-soluble thiophene-benzene based electrochromic polymers as electrode materials for supercapacitor

The bis(alkoxy) group para-substituted para-phenylene (p-phenylene) based conjugated polymers exhibit good electronic property due to the existence of intra-molecular non-covalent interaction between oxygen and heteroatom. However, the strong inter-molecular aggregation inhibits the ionic transport of polymer. Here, the strategy of changing side chain substitution position is employed to improve the properties of conjugated polymer. Three organic solvent-soluble conjugated polymers based on the bis(hexyloxy) group ortho-substituted p-phenylene were synthesized. The three polymers display small dihedral angles between thiophene and benzene. As the conjugated chain length of repeat units increasing, the redox potentials of polymers decrease gradually. From P1 to P2 to P3, their optical absorption regions red shift gradually, leading to neutral polymers display yellow for P1, orange for P2, magenta for P3, respectively. And the three polymers display good electrochromic properties (coloration efficiency: 641 cm2 C−1; response time: 0.2 s; optical contrast: 54%). Also, P2 possess the specific capacitance value of 170 F g−1, which is higher than that of most reported soluble conjugated polymers. Combining energy storage and electrochromic performance of the three polymers, their visualization monitor of energy storage were investigated.

Solvent-induced lengthened conjugated chains in electrochromic PEDOT for enhanced optical modulation

Conjugated PEDOT is considered as a promising electrochromic (EC) material, while the unsatisfactory optical modulation contrast limits its applications. Enhancing the conjugated chain length has been proved to improve the EC performance of conjugated conductive polymers (CPs). Herein, a simple and effective solvent-induced approach is developed to prepare EC PEDOT with extended conjugated chains. A strong polarity solvent of acetonitrile is employed to electrochemically polymerize PEDOT on a well-designed Ni(OH)2 nanosheet arrays substrate, which facilitates a longer conjugated chain formed in the PEDOT molecules. Compared with the samples obtained in water, the acetonitrile-assistant prepared PEDOT demonstrates a superior EC behavior, including enhanced transmittance contrast (∼48% at 550 nm), fast response for coloring/bleaching (1.35 s/0.83 s), ultrahigh coloration efficiency (293.6 cm2 C-1) and improved cycling durability. Particularly, a stable optical modulation could be maintained in a wide temperature range (−10 to 100 °C) and harsh acidity environment. This work is anticipated to provide a novel and simple approach to lengthen the conjugated chains of EC PEDOT toward enhanced optical modulation and can also be applicable to various conjugated CPs.

Chain-Length-Dependent Photophysical Properties of α,ω-Di(4-pyridyl)polyenes: Effects of Solvent Polarity, Hydrogen Bond Formation, Protonation, and N-Alkylation.

In this study, we investigated the solvent effects on the photophysical properties of α,ω-di(4-pyridyl)polyenes 1-5 having 1-5 double bonds. The solution photoproperties depend strongly on conjugation chain length. The absorption maximum (λa) of dipyridylethylene 1 is observed at around 290 nm and only slightly redshifts as the solvent polarity increases, whereas its fluorescence maximum (λf) redshifts from 368 nm in hexane to 403 nm in acetonitrile. Although 1 is a centrosymmetric molecule, its fluorescence energy linearly correlates with the Onsager solvent polarity function f(ε) - f(n2) = (ε - 1)/(2ε + 1)-(n2 - 1)/(2n2 + 1), indicating that the emission originates from an intramolecular charge transfer (CT) excited state. Exceptionally, λf in methanol is largely blue-shifted to 341 nm from those in other aprotic solvents. The fluorescence solvatochromism of longer polyenes 2-5 is much less significant than that of 1. Upon protonation and N-alkylation, both the absorption and fluorescence spectra of all five compounds are red-shifted in methanol. The largest shifts in λa and λf on protonation are observed for pentaene 5 (73 nm) and diene 2 (57 nm), respectively.

Regulating monomer assembly to enhance PEDOT capacitance performance via different oxidants

The development of poly(3,4-ethylenedioxythiophene) (PEDOT) with high specific capacitance is the key to pursuing high-performance supercapacitors, and the electrochemical properties of PEDOT are closely related to the oxidation degree and conjugated chain length of its molecular chain. In this work, the influences of various oxidants (FeCl3, Fe(Tos)3 and MoCl5) on the molecular chain structure and capacitive properties of PEDOT via vapor phase polymerization were systematically investigated. Fe(Tos)3 can significantly improve the degree of oxidation and the length of the conjugated chain of PEDOT compared to FeCl3 and MoCl5, enhancing the conductivity and providing more active sites for Faraday reaction. Therefore, the PEDOT/P(Fe(Tos)3) electrode displays a considerable conductivity of 73 S cm-1, high areal capacitance (419 mF cm-2) and excellent electrochemical stability under the different bent state. Moreover, the conjugated structure strengthens the interaction between PEDOT chains, achieving good cycle stability. Therefore, Fe(Tos)3 is an ideal oxidant for obtaining high-performance PEDOT electrode materials.

Synthesis of 4-(5-Nitrophenylfur-2-yl)-1,2,3-thia- and Selenadiazoles

Arylation of 2-acetylfuran with o-, m-, and p-nitrophenyldiazonium salts under the conditions of the Gomberg-Bachmann reaction has afforded the corresponding 5-(nitrophenyl)-2-acetylfurans. Their carbo-ethoxyhydrazones have undergone the cyclization into stable 4-(5-nitrophenylfur-2-yl)-1,2,3-thiadiazoles under the conditions of the Hurd-Mori reaction. Analogous semicarbazones have afforded the corresponding selenadiazoles upon oxidation with selenium dioxide. The analysis of electronic absorption spectra of the obtained hybrid heterocycles has shown that the conjugation of the phenyl and the furan ring in o-nitrophenyl derivatives is distorted due to steric hindrance, whereas the effect of direct polar conjugation leading to strong bathochromic shift of the absorption band has been observed in the case of the p-nitro derivatives. The position and intensity of the bands in the electronic absorption spectra of the studied compounds are determined by electronic as well as steric factors. The difference in the length of conjugation chain determined by the position of the nitro group in the phenyl fragment also contributes to the observed trend. The introduction of selenadiazole fragment instead of thiadiazole one has caused slight bathochromic shift of the band in the electron absorption spectra.

One-step facile synthesis of poly(N-vinylcarbazole)-polypyrrole/graphene oxide nanocomposites: enhanced solubility, thermal stability and good electrical conductivity

Poly (N-vinylcarbazole)-polypyrrole/graphene oxide (PNVC-Ppy/GO) nanocomposites have been successfully prepared by one-step chemical oxidative polymerization using ferric chloride hexahydrate in the presence of dodecyl benzene sulfonic acid. The composite formation, morphology and the crystallinity of the composite have been characterized by FTIR spectroscopy, FESEM, and XRD, respectively. The incorporation of graphene oxide into the PNVC-Ppy matrix induces interaction between graphene oxide and PNVC-Ppy via hydrogen bonding and π–π* stacking. This π–π* stacking between the GO layers and PNVC-Ppy produces longer conjugation length leading to a higher solubility in organic solvents and enhanced electron mobility. The information of conjugation chain length and charge transfer capacity at the interface of the composite has been obtained from the Raman spectroscopy and photolumincience spectroscopy. The improved thermal stability and electrical d.c. conductivity (0.123 S/cm) of the resulting PNVC-Ppy/GO composite compared to the PNVC–Ppy copolymer (0.08 S/cm) is attributed to the incorporation of graphene oxide in the composite.

Effect of Linking Pattern of Dibenzothiophene-S,S-dioxide-Containing Conjugated Microporous Polymers on the Photocatalytic Performance

Conjugated microporous polymers (CMPs) exhibit great potential for photocatalytic hydrogen generation due to their tunable electronic structure. The rational molecular design is a key point for developing an efficient CMP photocatalyst. Herein, we developed two CMPs photocatalysts via the copolymerization from pyrene and dibenzothiophene-S,S-dioxide building blocks. The effect of the linking pattern of the building block of dibenzothiophene-S,S-dioxide on the photocatalytic hydrogen evolution was explored. The polymer of PyDOBT-1 with 3,7-linking pattern shows a superior photocatalytic performance to PyDOBT-2 with 2,8-linking pattern because the 3,7-linking pattern enhances the conjugation chain length and improves the coplanarity of the polymeric backbone, which facilitate the charges migration along the polymer chain. As a result, the bare PyDOBT-1 shows an impressive visible light activity with a hydrogen evolution rate (HER) of 5697 μmol h–1 g–1. Notably, an outstanding HER of 12986 μmol h–1 g–1 was a...

Increase of polymeric chain conjugation length in UV irradiated monolayer of hydroxyalkadiynyl N-arylcarbamate derivative

Photopolymerization of Langmuir–Schaefer monolayers of 12-hydroxy-7,9-dodecadiyn-1-yl N-(4-methoxyphenyl)carbamate molecules under long-term UV irradiation provided the new polymer material. The observed blue phase polymer absorption band shift (∼30 nm) to the longer wavelengths during the sample UV irradiation corresponds to a continuous increase of the polymeric chain conjugation length. The morphology of mono-layers was determined by the scanning electron microscopy.

Unified analysis of optical absorption spectra of carotenoids based on a stochastic model

The chemical structures of the carotenoid molecules are very simple and one might think that their electronic features are easily predicted. However, there is still has so much unknown information excepting the correlation between the electronic energy state and the length of effective conjugation chain of carotenoids. To investigate the electronic feature of the carotenoids, the most essential method is measuring the optical absorption spectra, but simulations based on the resonance Raman spectra are also an effective approach. For this reason, we studied the optical absorption spectra as well as resonance Raman spectra of 15 different carotenoid molecules each possessing a cyclic end-group, recorded in tetrahydrofuran (THF) solutions at room temperature. The whole band shapes of the absorption spectra of all these carotenoid molecules were successfully simulated using a stochastic model and Brownian oscillators. The parameters obtained from the simulation make it possible to discuss the intermolecular interaction between carotenoids and solvent THF molecules quantitatively.

Facile way to prepare one dimensional Ag@oligoaniline wires

Abstract Silver wires (SWs) are directly prepared from aqueous silver nitrate by depositing reduced silver nano-particles (AgNPs) on the self-assembled, 1-D wires of the nitric acid doped tetraanilines (TeAN-ES) which also behave as the reducing agent. The molecular weights (MW) of most of the TeAN-ES after the redox reaction are found to be doubled, obtained from the matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) and gel permeation chromatography (GPC) spectra. The doubled MW attributed to the head-to-head coupling of TeAN-ES molecules, resulting in the formation of octaaniline (OcAN) during the redox reaction and the functional group that connects two TeAN-ES molecules is characterized as doped phenazine by IR-spectrum. The extended conjugation chain length from TeAN-ES to OcAN is confirmed by the additional λ max peak in the near-IR range. AgNPs were obtained from the redox reaction between Ag + and 1-D, self-assembled TeAN-ES which is covered with deposited AgNPs, leading to the formation of both SWs and OcANs. The mixture eventually becomes networks of non-woven fabric made of Ag@oligoaniline wires which also induce the plummeting resistance of the mixture.

Surface functionalization of cellulose with poly(3-hexylthiophene) via novel oxidative polymerization

Surface functionalization of cellulose with poly(3-hexylthiophene) (P3HT) was conducted with FeCl3 as an oxidant in three different solvents: acetonitrile, chloroform, and hexane. Of these three solvents, hexane best promoted the grafting P3HT to cellulose with a high grafting ratio and molecular weight. The maxima of the UV–vis absorption and fluorescent spectra, observed at around 500 and 600nm, respectively, represented the build-up of the conjugated chain length formed by the grafting of P3HT onto the cellulose surface. The HOMO level of cellulose as determined by photoemission yield spectroscopy decreased from 4.83 to 4.67eV after modification with P3HT. Grafting P3HT onto the surface of cellulose provided super-hydrophobic property with a lotus effect. The conductivity of cellulose also improved significantly, from 10−9 to 10−6S/cm when P3HT was present on the surface. The thermal stability and crystallinity of cellulose decreased slightly upon graft polymerization with P3HT.

The evolution of organic thermoelectric material based on conducting poly(3,4-ethylenedioxythiophene)

Thermoelectric (TE) material, as one of new energy materials, is regarded as one of the most important energy-saving materials, which can directly achieve the interconversion between heat and electricity. Presently, inorganic semi-conductors are considered to be the best thermoelectric materials. However, the development of new thermoelectric material has attracted great attention owing to the scarce resource and limited performance of inorganic thermoelectric materials. As the discovery and wide application of conducting polymers (CPs), organic thermoelectric materials have come into the sights of people over the past 30 years. The development of CPs as a promising thermoelectric material has gained great attention over the past decades. Various CPs have been developed and investigated on thermoelectric performance such as polyacetylene (PA), polyaniline (PANi), polypyrrole (PPy), polythiophene (PTh) and their derivatives since 1989. Among numerous CPs, poly(3,4-ethylenedioxythiophene) (PEDOT) shows many superior properties compared to others due to its excellent environmental stability, water solubility, easy processibility, and high electrical conductivity, which brings new strategy for studies of high performance organic thermoelectric materials. The conductive PEDOT combined with an insulating poly(styrenesulfonate) (PSS) can form a stable aqueous PEDOT:PSS with a good film-forming property and has been regarded as one of the most potential thermoelectric material. In 2008, the thermoelectric performance of PEDOT:PSS pellets were reported systematically for the first time. Although its thermoelectric figure-of-merit ( ZT ) was as low as 10 - 3, it was one of the highest values for CPs at that time. Soon afterwards, the thermoelectric performance of the free-standing PEDOT:PSS film achieved a ZT value as high as 10 - 2 in 2010. During these years, great attention focused on the derivatives of PTh, polyselenophene (PSh), PANi, and polycarbazole (PCz). Since 2010, PEDOT:PSS has come into sight of researchers in the world. The past few years witnessed great development of thermoelectric performance of conducting PEDOT:PSS ( ZT ~10 - 1). In recent ten years, the thermoelectric figure-of-merit ( ZT ) of PEDOT has been enhanced by three orders of magnitude from 10 - 4 to 10 - 1 as one of the most promising organic thermoelectric materials. Presently, the enhanced thermoelectric performance for PEDOT concern in the increased electrical conductivity via an easy method, especially for PEDOT:PSS. A large electrical conductivity of PEDOT:PSS thin film more than 3000 S cm - 1 has been achieved by adding an organic solvent or post-treatment with organic solvents, acid, and ionic liquids. Compared to inorganic thermoelectric materials, PEDOT:PSS can achieve a high electrical conductivity without an obviously decreasing Seebeck coefficient. A further improvement of thermoelectric performance for PEDOT:PSS has been devoted to the optimization of Seebeck coefficient via the pH value adjustment, the reduction of the oxidized level of conductive PEDOT, or composite with inorganic thermoelectric materials. A large thermoelectric power factor has become a reality. Although there are large gaps from actual industrial application for thermoelectric PEDOT ( ZT ˃1), yet most efforts focus on the high performance PEDOT. A large number of new techniques and methods have been developed to improve the thermoelectric performance of PEDOT. This review pays the attention to the advantages and characteristics, development history, and performance improvement of PEDOT as a promising organic thermoelectric CP from discovery to development. In order to achieve a high performance thermoelectric PEDOT, more attention should be paid to the development of low dimensional PEDOT crystal, control of oxidized level, extension of conjugated chain length of PEDOT, new preparation method and techniques, and the effects of crystal structure on electron transport properties as well as the flexible PEDOT thermoelectric devices in the future. Additionally, it is necessary to keep up with the development of n-type organic thermoelectric materials.

Donor-Acceptor Conjugated System: A Neutral Hydrophobic Fluorescence Probe

Fluorescence probe with intramolecular charge transfer behavior has received a great deal of attention in recent years Such molecule is highly sensitive to its local environment and plays critical role in many industrial and biological applications Donor acceptor conjugated systems based on diphenylpolyene are one of such example The presence of conjugated chain length and the donor acceptor substituent rsquo s at the appropriate position allows the molecule to cover a wide range of absorption and fluorescence wavelength and hence the optical property of the molecule is attenuated easily Thus diphenylpolyenes are suitable candidate for various fluorescence probe applications The above mentioned aspects have been discussed and summarized in this paper

Analysis of the electronic, IR, and 1H NMR spectra of conjugated oligomers based on 4,4'-triphenylamine vinylene

Two types of conjugated oligomers based on 4,4'-triphenylamine vinylene have been synthesized and characterized by the methods of IR, UV–visible, and 1H NMR spectroscopy. The corresponding spectra have also been simulated theoretically at the density functional theory level with application of the B3LYP and BMK hybrid exchange-correlation functionals. A comparative analysis of the experimental and theoretical spectra of polymers and oligomers has revealed regularities of the manifestation of spectral signals depending on the conjugation chain length and the presence of a substituent in the triphenylamine core. It has been established, in particular, that the absolute intensity of IR bands satisfies a linear dependence with increase in the degree of polymerization; however, no frequency shift is observed at the same time. The position of the main peak in electron absorption spectra demonstrates the bathochromic shift with an increase in the oligomeric chain length due to the narrowing of the energy gap between the boundary molecular orbitals. Based on the theoretical estimation of the hydrogen atoms chemical shifts, the signals of various protons types in the strongly broadened experimental 1H NMR spectra of the bis-(4-iodine phenyl)-phenylamine and N,N-bis-(4-iodine phenyl)-4'-(phenylethynyl)-phenylamine polymerization products have also been identified.

The Influence of the Molecular Structure of Cyanine Dye on the Component Composition of Molecular Layers

The formation of the component composition of symmetric cationic cyanine dyes on glass is studied. The absorption spectra of layers of three homologous series of dyes with end heterocyclic groups of different spatial and chemical compositions are measured, and the absorption spectra of monomer components and aggregates are separated. The component compositions of layers of different thicknesses are compared. It is shown that the widening of the absorption spectra of molecular layers against the spectra of ethanol solutions of these compounds is caused mainly by the formation of various monomer stereoisomers and molecular aggregates and their interaction with the substrate surface and the neighborhood. The number of isomer forms and their relative concentrations depend on the layer thickness, the electron donor ability and spatial structure of end groups, and the cation conjugation chain length. The influence of the anion manifests itself only in the concentration ratio of the formed monomers and a small shift of the maxima of their absorption bands. The increase in the number of monomer forms produced in the layer corresponds to the increase in the conjugation chain length. Spatial obstacles created by heterocyclic groups inhibit the formation of definite stereoisomers, which reduces the number of components of the layer.