Position Of Substituents Research Articles

Switching the regioselectivity of acid-catalyzed reactions of arylnaphtho[2,1-b]furans via a [1,2]-aryl shift.

The [1,2]-aryl shift reaction was used to synthesize naphtho[2,1-b]furans as promising fluorescent scaffolds for organic electronics. The target compounds are furan analogues of phenanthrene formally accessed by isosteric replacement of the CHCH moiety with an oxygen atom. The straightforward and robust approach involving a [1,2]-aryl shift as a key step provides easy access to a wide range of naphtho[2,1-b]furans with the possibility of late-stage functionalization. Efficient switching of the regioselectivity of acid-catalyzed reactions of arylnaphtho[2,1-b]furans via a [1,2]-aryl shift has been demonstrated. A one-pot protocol involving sequential intramolecular condensation/[1,2]-aryl shift/intermolecular oxidative aromatic coupling to provide access to binaphtho[2,1-b]furan analogues of BINOL was developed. The advantage of these compounds lies in the strong variation in chemical properties and spectral performance depending on the nature and position of the aryl substituent, which facilitates the synthesis of compounds with desired spectral characteristics and opens up prospects for their further use in electronics, biotechnologies and organic synthesis.

The effects of alkyl substitution on the aggregation of π-conjugated dyes: spectroscopic study and modelling.

A family of dithienosilole-based dyes with alternating donor and acceptor conjugated groups, decorated with linear or branched alkyl chains at different positions on the backbone, have been obtained and investigated in different aggregation states. These dyes are characterized by almost panchromatic absorption and by near-IR emission, with good quantum yields in a variety of solvents with different polarity. We demonstrate that the nature and position of the alkyl substituents strongly govern the self-assembly of the dyes, whose packing is also sensitive to external stimuli, such as grinding and water addition. Thanks to computational results and theoretical modelling, we are able to interpret the results based on two possible preferential packings, characterized by distinct spectroscopic behaviour, whose abundance can be tuned according to the nature and position of the alkyl chains, as well as via external stimuli.

Synthesis and physical properties of tunable aryl alkyl ionic liquids based on 1-aryl-4,5-dimethylimidazolium cations.

We present a new class of tunable aryl alkyl ionic liquids (TAAILs) based on 1-aryl-4,5-dimethylimidazolium cations with electron-withdrawing and -donating substituents in different positions of the phenyl ring and the bis(trifluoromethylsulfonyl)imide (NTf2) anion. We investigated the effect of additional methyl groups in the backbone of the imidazolium core on the physical properties regarding viscosity, conductivity and electrochemical window. With an electrochemical window of up to 6.3 V, which is unprecedented for TAAILs with an NTf2 anion, this new class of TAAILs demonstrates the opportunities that arise from modifications in the backbone of the imidazolium cation.

Supercapacitive properties of carbazole-containing cobalt(II) phthalocyanines/reduced graphene oxide composites.

This study aims to compare the effect of substituents (position and number) and reduced graphene oxide on the supercapacitive properties of cobalt(II) phthalocyanines. For this purpose, three new tetra- and octa-substituted cobalt(II) phthalocyanines bearing 9H-carbazol-2-yloxy groups on peripheral or non-peripheral positions (1-3) were synthesized. The characterization of the resultant cobalt(II) phthalocyanines was carried out by applying several spectroscopic approaches. The newly synthesized macromolecules were used for the functionalization of reduced graphene oxide (rGO). The obtained nanocomposites (rGO-(1-3)) were utilized for the modification of Ni foam (NiF) electrodes through a facile one-step electrodeposition strategy performed for electrochemical supercapacitor applications. Simultaneous polymerization of the cobalt phthalocyanines and electrochemically reduction of graphene oxide led to the formation of a fabricating layer on the surface of the NiF electrode. The resulting electropolymerized films were characterized by Raman, Fourier-transform infrared (FT-IR), and Field emission scanning electron microscope (FESEM) spectroscopic techniques as well as electrochemical methods. The prepared electrodes possessed superior electrochemical activities owing to the synergistic effect of the cobalt(II) phthalocyanines and rGO. All the modified electrodes displayed high supercapacitaive properties and the highest activity was obtained for the NiF/rGO2-1 electrode. The NiF/rGO2-1 electrode exhibited higher specific capacitance (655.2 F g-1 at 0.5 A g-1) than NiF/1 (338.0 F g-1). Additionally, a specific capacitance of 85.2% was obtained for NiF/rGO2-1 electrode after 3000 charge-discharge cycles. As a result, all the prepared metallophthalocyanines-reduced graphene oxide can be considered alternative agents to develop high performance-next-generation energy storage devices.

Substituent effects on the selectivity of ambimodal [6+4]/[4+2] cycloaddition.

In this work, we report a density functional theory (DFT) study and a dynamical trajectory study of substituent effects on the ambimodal [6+4]/[4+2] cycloaddition proposed for 1,3,5,10,12-cycloheptadecapentaene, referred to as cycloheptadecapentaene. The proposed cycloaddition proceeds through an ambimodal transition state, which results in both a [6+4] adduct a [4+2] adduct directly. The [6+4] adduct can be readily converted to the [4+2] adduct via a Cope rearrangement. We study the selectivity of the reaction with regard to the position of substituents, steric effects of substituents, and electronic effects of substituents. In the dynamical trajectory study, we find that nitro-substituted reactants lead to a new product from the ambimodal transition state via the hetero Diels-Alder reaction, and this new product can then be converted to a [4+2] adduct by a hetero [3, 3]-sigmatropic rearrangement. These results may provide insights for designing more bridged heterocyclic compounds.

Impact of substituent position on crystal structure and photoconductivity in 1D and 2D lead(ii) benzenethiolate coordination polymers

We revealed the relationship between the inorganic (–M–S–)n network and photoconductivity by systematically synthesizing semiconductive Pb(ii) coordination polymers with methoxybenzenethiol.

Rhodanine-based 4-(furan-2-yl)benzoic acids as inhibitors of xanthine oxidase

A series of rhodanine derivatives bearing 4-(furan-2-yl)benzoic acid moiety were synthesized and studied as inhibitors of xanthine oxidase. This enzyme is a known target for allopurinol and febuxostat used in the treatment of hyperuricemia, gout, and other diseases. The synthesized compounds with different substituents in position 3 of the rhodanine ring showed in vitro inhibitory activities towards xanthine oxidase in a low micromolar concentration range. The 4-(furan-2-yl)benzoic acid derivative with a fragment of N-unsubstituted rhodanine was found to have the lowest IC50 value which does not depend on the presence of albumin or Tween-80 under the assay conditions. According to kinetic data, the rhodanine-based 4-(furan-2-yl)benzoic acid was a mixed-type inhibitor with the same affinity for the free enzyme and the enzyme-substrate complex. Molecular docking and molecular dynamic studies were performed to elucidate the binding mode of this compound in the active site of xanthine oxidase

Effects of substitution and conjugation on photophysical properties of ESIPT-based fluorophores with the core of 4-aminophthalimide

4-Aminophthalimide is a highly fluorescent signaling unit with excellent photophysical properties and wide application foregrounds. Based on this, a range of theoretical investigations are conducted on the fluorescent probe (E)-5-((2-hydroxybenzylidene) amino) isoindoline-1, 3-dione (HID) with the core of 4-aminophthalimide using density functional theory (DFT) and time-containing density functional theory (TD-DFT) methods in this paper. The optimized configurations, vertical excitation and emission energies, electronic characteristics and excited-state intramolecular proton transfer (ESIPT) behaviors of the probe HID are discussed in detail. Furthermore, to enhance the luminescent properties of HID, five novel compounds have been designed based on the structure of HID by introducing amino, methoxy and naphthalene groups (–NH2, –OMe and C10H8). Our work thoroughly explores how the property and position of substituents and conjugation affect photophysical characteristics and ESIPT processes. We find that the ESIPT dynamics can be modulated by the substitution and conjugation effects. Specifically, the introduction of amino and methoxy groups at the ortho-position and the introduction of the naphthalene group promote the ESIPT behavior of HID1, whereas the introduction of amino and methoxy groups at the meta-position exhibits the contrary impact. Therefore, we boldly infer that the introduction of electron-donating groups in the ortho-position and the introduction of the conjugated group make the ESIPT process more effortless to occur, whereas the introduction of substituents with opposing natures in the meta-position makes the ESIPT process more difficult to occur. In addition, the ionization potentials (IP), electron affinities (EA) and reorganization energies (λh and λe) of molecules are calculated to assess their potential as luminescent materials. Our work not only reveals the luminescence and ESIPT mechanism of the probe HID1, but also proposes to modulate the ESIPT process through the substitution and conjugation effects. In particular, the designed molecules have better photoelectric properties as a result of their red-shifted absorption and fluorescence spectra, smaller energy gaps, larger transferred charges and greater charge transferred distances, which offers some valuable ideas for the experimental development of more efficient organic luminescent materials with ESIPT properties.

Influence of the structure of quinoline derivatives on their sorption on hypercrosslinked polystyrene

The article is devoted to the study of the chromatographic behaviour of quinoline and tetrahydroquinoline derivatives. The purpose of the study was to investigate the patterns of sorption of these compounds from aqueous-acetonitrile solutions on hyper-cross-linked polystyrene using reverse-phase high-performance liquid chromatography. The volume, polarizability, lipophilicity, and dipole moment of molecules of quinoline derivatives were calculated, which significantly depended on the nature and position of functional groups and substituents in the main nucleus. It has been established that the appearance of functional groups and substituents leads to an increase in the volume and polarizability of the molecules of quinoline derivatives compared to unsubstituted quinoline and methylquinoline, while the lipophilicity and dipole moment change depending on the nature of the substituent and its position in the main fragment. The dependences of sorption characteristics on the structure and physicochemical properties of sorbates were obtained. It has been shown that, in accordance with the laws of the reversed-phase version of liquid chromatography, the retention of substances changes symbatically with the change in the characteristics of the molecules responsible for dispersion interactions. In this case, the presence in the molecules of halogen atoms, phenyl radicals and other substituents capable of π-interactions with the surface of hyper-cross-linked polystyrene led to a significant increase in retention, and the presence of a carboxyl group or carboxyalkyls prone to interaction with the polar eluent significantly weakens retention. The appearance of an ester group in sorbate molecules generally significantly increased the volume, polarizability and lipophilicity of the corresponding derivatives, but had virtually no effect on retention, and therefore it was suggested that the presence of a carbonyl oxygen atom, capable of interacting with the polar components of the eluent, neutralizes the effect of physical-chemical factors that determine the sorption of these substances due to dispersion interactions. Thus, despite the symmetry in changes in the physicochemical parameters of the studied compounds and their retention, there was no strict proportionality, since, on the one hand, the retention of sorbates was carried out in accordance with the change in their physicochemical parameters, and on the other hand, it was determined by the tendency molecules of these compounds to competitive interactions with the components of the mobile phase. The presented results of the study can be useful in the development and optimization of methods for analysing compounds with similar structures, as well as for developing the theory of sorption of polyfunctional compounds from multicomponent solutions and establishing the relationship between sorption characteristics, other physicochemical parameters and the structure of molecules.

Substituent Positioning Effects on the Magnetic Properties of Sandwich-Type Erbium(III) Complexes with Bis(trimethylsilyl)-Substituted Cyclooctatetraenyl Ligands.

Lanthanide complexes with judiciously designed ligands have been extensively studied for their potential applications as single-molecule magnets. With the influence of ligands on their magnetic properties generally established, recent research has unearthed certain effects inherent to site differentiation due to the different types and varying numbers of substituents on the same ligand platform. Using two new sandwich-type Er(III) complexes with cyclooctatetraenyl (COT) ligands featuring two differently positioned trimethylsilyl (TMS) substituents, namely, [Li(DME)Er(COT1,5-TMS2)2]n (Er1) and [Na(DME)3][Er(COT1,3-TMS2)2] (Er2) [COT1,3-TMS2 and COT1,5-TMS2 donate 1,3- and 1,5-bis(trimethylsilyl)-substituted cyclooctatetraenyl ligands, respectively; DME = 1,2-dimethoxyethane], and with reference to previously reported [Li(DME)3][Er(COT1,4-TMS2)2] (A) and [K(DME)2][Er(COT1,4-TMS2)2] (B), any possible substituent position effects have been explored for the first time. The rearrangement of the TMS substituents from the starting COT1,4-TMS2 to COT1,3-TMS2 and COT1,5-TMS2, by way of formal migration of the TMS group, was thermally induced in the case of Er1, while for the formation of Er2, the use of Na+ in the placement of its Li+ and K+ congeners is essential. Both Er1 and Er2 display single-molecule magnetic behaviors with energy barriers of 170(3) and 172(6) K, respectively. Magnetic hysteresis loops, butterfly-shaped for Er1 and wide open for Er2, were observed up to 12 K for Er1 and 13 K for Er2. Studies of magnetic dynamics reveal the different pathways for relaxation of magnetization below 10 K, mainly by the Raman process for Er1 and by quantum tunneling of magnetization for Er2, leading to the order of magnitude difference in magnetic relaxation times and sharply different magnetic hysteresis loops.

Air- and Water-Stable Heteroleptic Copper (I) Complexes Bearing Bis(indazol-1-yl)methane Ligands: Synthesis, Characterisation, and Computational Studies.

A series of four novel heteroleptic Cu(I) complexes, bearing bis(1H-indazol-1-yl)methane analogues as N,N ligands and DPEPhos as the P,P ligand, were synthesised in high yields under mild conditions and characterised by spectroscopic and spectrometric techniques. In addition, the position of the carboxymethyl substituent in the complexes and its effect on the electrochemical and photophysical behaviour was evaluated. As expected, the homoleptic copper (I) complexes with the N,N ligands showed air instability. In contrast, the obtained heteroleptic complexes were air- and water-stable in solid and solution. All complexes displayed green-yellow luminescence in CH2Cl2 at room temperature due to ligand-centred (LC) phosphorescence in the case of the Cu(I) complex with an unsubstituted N,N ligand and metal-to-ligand charge transfer (MLCT) phosphorescence for the carboxymethyl-substituted complexes. Interestingly, proper substitution of the bis(1H-indazol-1-yl)methane ligand enabled the achievement of a remarkable luminescent yield (2.5%) in solution, showcasing the great potential of this novel class of copper(I) complexes for potential applications in luminescent devices and/or photocatalysis.

Efficient copolymerization of ethylene with norbornene mediated by phosphine-sulfonate palladium catalysts

A series of tBu-/Ar-substituted phosphine-sulfonate palladium catalysts Pd1-Pd6 {[κ2(P, O)-(tBu)ArP(C6H4SO2O)]Pd(Me)(DMSO)} (1: Ar = Ph; 2: Ar = 4-OMe-C6H4; 3: Ar = 4-CF3-C6H4; 4: Ar = 2-OMe-C6H4; 5: Ar = 2,5- (OMe)2-C6H3; 6: Ar = 2,4-(OMe)2-C6H3) were prepared to copolymerize ethylene with norbornene and its polar derivatives. Installing electron-donating OMe substituent on the nonchelating P-bound aryl was proven to enhance the properties of catalysts. The position and number of OMe substituent significantly influenced the copolymerization results. The E-NB copolymers generated from these catalysts showed both high comonomer incorporations (≥19.3 mol%) and high copolymer molecular weights (≥24.6 kg⋅mol−1), which has been proven to be difficult to achieve using this catalyst system. And for the obtained copolymers, their norbornene incorporations and Tg values conformed to a linear relationship. More importantly, these catalysts can efficiently mediate the copolymerizations of ethylene and polar norbornenes, along with high activities (up to 1.0 × 106 g⋅mol−1⋅h−1), high molecular weights (up to 182 kg⋅mol−1), and high incorporations (up to 36.7 mol%). This work provided an efficient method to synthesis cyclic olefin copolymer using late transition metal catalysts.

Elongation of N6-benzyladenosine scaffold via Pd-catalyzed C–C bond formation leads to derivatives with antiflaviviral activity

Decoration of nucleoside analogues with lipophilic groups often leads to compounds with improved antiviral activity. For example, N6-benzyladenosine derivatives containing elongated lipophilic substituents in the benzyl core efficiently inhibit reproduction of tick-borne encephalitis virus (TBEV), while N6-benzyladenosine itself potently inhibits reproduction of human enterovirus A71 (EV-A71). We have extended a series of N6-benzyladenosine analogues using effective synthetic methods of CC bond formation based on Pd-catalyzed cross-coupling reactions (Sonogashira and Suzuki) in order to study the influence of bulky lipophilic substituents in the N6 position of adenosine on the antiviral activity against flaviviruses, such as TBEV, yellow fever virus (YFV) and West Nile virus (WNV), as well as a panel of enteroviruses including EV-A71, Echovirus 30 (E30), and poliovirus type 2 (PV2). Reproduction of tested flaviviruses appeared to be inhibited by the micromolar concentrations of the compounds, while cytotoxicity in most cases was beyond the detection limit. Time-of-addition studies demonstrated that the hit compounds inhibited the stage of viral RNA synthesis, but not the stages of the viral entry or protein translation. As a result, several new promising antiflaviviral leads have been identified. On the other hand, none of the synthesized compounds inhibited enterovirus reproduction, indicating a possibility of involvement of flavivirus-specific pathways in their mechanism of action.

Inhibition of Xanthine Oxidase by Pyrazolone Derivatives Bearing a 4-(Furan-2-yl)benzoic Acid Moiety

The pyrazolone-based 4-(furan-2-yl)benzoic acids have been synthesized and studied as xanthine oxidase inhibitors. This enzyme is one of the therapeutic targets for the treatment of hyperuricemia and related diseases. The compounds studied have found to exhibit low micromolar IC50 values relative to the enzyme in vitro, depending on substituents in position 3 of the pyrazolone ring. However, the inhibitory effects observed are reduced in the presence of bovine serum albumin or Tween-80. Among the pyrazolone derivatives synthesized, 4-(5-((3-methyl-5-oxo-1-phenyl-1,5-dihydro-4H-pyrazol-4-ylidene)methyl)furan-2-yl)benzoic acid has been found to be the most potent inhibitor of xanthine oxidase. Kinetic results have shown that this compound is a mixed-type inhibitor with higher affinity to the free enzyme than to the enzyme-substrate complex. The results of the molecular docking and molecular dynamics show that the carboxylic group of the inhibitor can form a salt bridge with Arg880 and a hydrogen bond with Thr1010. These interactions can be key factors in the enzyme-inhibitor complex stabilization.

The effect of substituent position and solvent on thermal Z‒E isomerization of dihydroquinolylazotetrazole dyes: kinetic, thermodynamic, and spectral approaches.

Kinetic and thermodynamic parameters have been investigated for the thermal Z‒E isomerization of dihydroquinolylazotetrazole dyes with alkyl substituents (Me, t-Bu, and Adm) at positions 1 (dyes 2) and 2 (dyes 3) of the tetrazole moiety in two solvents of different polarity, acetonitrile (MeCN) and toluene. The experimental results show crucial dependence of these parameters on a substituent position in the tetrazole moiety and on a solvent. For dyes 2, Eact and ΔH‡ are lower in MeCN than in toluene that results in a high increase in the lifetimes of the Z isomers: from milliseconds in MeCN to minutes in toluene. For dyes 3, the difference in Eact and ΔH‡ in the two solvents is opposite: Eact and ΔH‡ are by more than 20kJmol-1 higher in MeCN, nevertheless, the rate constants for 3 in toluene are comparable with those in MeCN at the ambient temperature and the difference in the behavior is determined by the value of negative entropy of activation. Quantum-chemical calculations of the thermal Z‒E isomerization show the possibility of the process to occur via crossing from the S0 to the thermally induced T1 state. The contribution of this path is highest for 3 in toluene. The analysis of the absorption spectra demonstrates that for the E isomers, the n‒π* and π‒π* transitions are within the long-wavelength absorption band and their positions relative each other are opposite in the solvents: the n‒π* transition is blue-shifted relative to the π‒π* transition in MeCN and is red-shifted in toluene.

Fluorescent properties in solid-state and solution of novel tricyclic derivatives of chloro/bromophenylchromanones and 2-methylpyrazoline

In this work, we reported the synthesis and spectroscopic characterization of seven novel tricyclic compounds resulting from the reaction of 3-benzylidenechromanone with Cl or Br substituent in different positions and without halogen with methylhydrazine. The structural characterization of compounds was done through different techniques i.e., FTIR,1HNMR,a single and powder X-Ray diffraction. Moreover, fluorescence quantum yield and lifetime assessed their fluorescent properties in the solid state and various solvents. Derivatives with Cl or Br substituent in positions 2 and 4 are isostructural. 4-Cl, 4-Br and 3-Cl compounds exhibit fluorescence with moderate efficiency (quantum yield 0.11–0.26) in solid state due to specific arrangements, so-called π-stack brick stone with head-to-tail self-assembly. Other crystalline compounds (2-Cl, 2-Br and 3-Br) that exhibit negligible fluorescence quantum yield have crossed V-type arrangement. In the solution, the nonhalogenated compound shows the best fluorescence efficiency. In turn, the presence of halogen atoms results in fluorescence decreasing. TD-DFT study revealed that unsubstituted compound higher emissive in solution has a different electron density distribution at HOMO and LUMO levels than less emissive substituted compounds (A3 and A3).

Photophysical properties of 3-arylthioimidazo[1,2-a]pyridine derivatives: The role of peripheral electron-donating and electron-withdrawing groups in the advance of organic materials engineering

3-Arylthioimidazo[1,2-a]pyridine derivatives may present potential use in fields such as optoelectronics, organic light-emitting diodes (OLEDs), bioimaging, and may be employed as bioprobes in DNA and RNA. However, before these materials can be used for such applications, it is necessary to assess their photophysical properties. Here, we investigated the photophysical properties of five novel 3-arylthioimidazo[1,2-a]pyridine derivatives with different peripheral electron-withdrawing and electron-donating groups. The use of spectroscopic techniques, including UV–vis absorption, fluorescence, time-resolved fluorescence spectroscopy, combined with quantum chemical calculations, allowed us to gain a comprehensive understanding of the compounds' photophysical properties. The results revealed that the 3-arylthioimidazo[1,2-a]pyridine derivatives possess remarkable emissive properties, with a 4.5-fold increase when substituting the trifluoromethyl group for a methoxy group. Furthermore, it has been observed that the compounds containing peripheral groups with halogen atoms exhibit fluorescence quenching. The electron-withdrawing character of the imidazo[1,2-a]pyridine and the position of the lateral substituent hindered the impact of electron-withdrawing groups, while electron-donating groups enhanced the photophysical properties, resulting in increased Stokes shift, larger permanent dipole moment difference, and charge displacement. In conclusion, this study provides key insights into the photophysics of 3-arylthioimidazo[1,2-a]pyridine derivatives and the role of peripheral electron-donating and electron-withdrawing groups. These findings hold great potential for the advancement of optical materials and set foundation for future technological applications.

Cooordination compounds of Cu(II) and Bi(III) with aminopolycarboxylate ligands and 4-ethyl-, 4-phenyl- thiosesemicarbazones of 2-acetylpyridine

The paper deals with the synthesis and analysis of two series of homometallic coordination compounds with 2-acetylpyridine thiosemicarbazones, with different substituents in the N4 position, having the general formulas {Cu(4XAcpytsc)}2Cu(APC)·nH2O in case of Cu(II) and Bi(HAPC)(4XHAcpytsc)m·nH2O for Bi(III) ions. Targeting at getting synergistic effects, two series of heterometallic coordination compounds of general formula {Cu(4XAcpytsc)}Bi(APC)·nH2O with two aminopolycarboxylate ions have been synthesized (n=1-8; m = 1 or 2; APC = edta4-, cdta4-), (4XAcpytsc) monodeprotonated or non-protonated (4XHAcpysc) form of 4-ethyl- or 4-phenyl-thiosemicarbazones of 2-acetylpyridine (Acpytsc). The antioxidant property of the obtained homo- and heterometallic compounds was identified. The results have shown that the highest antioxidant property has the homometallic compound of Bi(III) with 2-acetylpyridine 4-phenyl-thiosemicarbazone and edta4- anion, with IC50 = 0,71 μM which is approximately 13 times higher than the free ligand and 56 times higher than the reference Trolox.

The cooperative effects of ligand substituent positions and solvents on spin crossover in Mn(III) complexes based on hexadentate Schiff-base ligands

Spin crossover (SCO), as a molecular bistable phenomenon, has attracted extensive interest. In this paper, the syntheses, crystal structures and magnetic properties of three Mn(III) hexadentate Schiff-base complexes [Mn(3-OMe-sal-N-1,5,8,12)]AsF6·H2O (1), [Mn(4-OMe-sal-N-1,5,8,12)]AsF6·H2O (2) and [Mn(5-OMe-sal-N-1,5,8,12)]AsF6(3) have been reported. The substituent positions of ligands and solvent molecules have a cooperative effect on SCO behavior. Complex 1 shows a complete SCO between the high-spin (HS, S = 2) and low-spin (LS, S = 1) states without thermal hysteresis, and complex 2 shows a gradual incomplete SCO behavior. The transition temperatures of 2 (T1/2 = 241 K) is 98 K higher than that of 1 (T1/2 = 143 K), which indicates that the ligand field strength of (4-OMe-sal-N-1,5,8,12)2– is stronger than that of (3-OMe-sal-N-1,5,8,12)2–. Due to the absence of crystallizing solvent water molecule, complex 3 maintains a HS state in the test temperature range.

Theoretical study of the effect of D-A type polymer donors on the performance of Y6-based organic solar cells

Non-fullerene organic solar cells (OSCs) based on Y6 molecule have developed rapidly in recent years, and the power conversion efficiency (PCE) varies greatly when the OSC device constructed by Y6 and donor molecules with small structural difference. In this work, the influence of six donor-acceptor (D-A) polymer donors on Y6-based OSCs were focused. The ground-state properties (planarity, frontier molecular orbital energy levels, driving force), excited-state properties of donors (primary indicators, Coulomb attraction) and donor/acceptor interfaces (Frenkel excitation (FE) and charge transfer (CT) states, electron coupling and charge separation rates) were discussed. The results show that symmetrical alkyl chains in the acceptor unit is favorable for maintaining planarity of molecule, while fluorination induces twisting in the thiophene bridge and acceptor unit. And the investigated high-performance molecules have desirable driving force, smaller Coulomb attraction and significant degree of holes and electrons delocalization. Also, the highest-performance system has multiple charge transfer pathways, which can improve charge separation efficiency. At the same time, high-performance systems often have better planarity and more favorable substituent positions. The high-performance donor/Y6 systems have more advantage in charge separation than the low-performance systems. This work provides a fundamental understanding of the impact of D-A type donor materials on the cell performance and theoretical guidance for further optimization of polymer donor materials in Y6-based OSCs.