Synthesis, characterization, surface analysis, optical activity and solvent effects on the electronic absorptions of Schiff base-functionalized amino thiophene derivatives: Experimental and TD-DFT investigations

New derivatives of 3,3′-di-(((E)-(5-substituted-thiophen-2-yl)methylene)amino)-N-methylpropylamines (3a,b) were synthesized from the dehydration of N-methyl-diaminopropylamine and 2-thielylcarboxaldehyde derivatives; spectroscopically characterized by 1H- and 13C-NMR, IR, LC-MS, UV-Vis and elemental analysis. The nature of the electronic transitions of the SB compounds was investigated using Time-Dependent Density-Functional Theory (TD-DFT). Surface analysis and influence of solvent polarity on spectral properties were examined and established consequently. The molecular electrostatic potential (MEP) revealed that the two geometrical structures were found to be quite similar in term of electronic distributions. The presence of different electrophilic and nucleophilic sites located on the surfaces was suggested to stabilize the structures via classical H-bond and non-classical C-H…π interactions, in addition to interact with assorted solvent molecules. On the other hand, the solvatochromism of compound 3b revealed a gradual shift to the red region through the increase of the solvent polarity, recording a 12 nm of bathochromic shift. The solvation relationship between the experimental λmax and Gutmann's donicity numbers displayed a sense of positive linear behavior with a fluctuation, which was ascribed to a week interaction between molecules of solute and selected solvent. The band gap energy of compound 3a was evaluated experimentally and computationally. Using optical absorption spectra, a value of ‒ 3.801 eV was estimated following Tauc approach, while ‒ 3.720 eV was resulting from TD-DFT simulation

New tetradentate Schiff base Cu(II) complexes: synthesis, physicochemical, chromotropism, fluorescence, thermal, and selective catalytic oxidation

Three neutral Cu(II)/ƞ4-NNNO Schiff base complexes (1-3) were prepared from the (E)-4-nitro-2-(((2-(piperazin-1-yl)ethyl)imino)methyl)phenol, tetradentate Schiff base (SB) ligand, and the corresponding copper(II) salts. The new SB and its complexes were fully characterized by CHN-EA, standard spectroscopic, thermal, and fluorescence analyses. The formation of the complexes was monitored by EDX, FT-IR, and UV-Vis. The chromotropism studies of the complexes reflected remarkable findings, in which bathochromic solvato- and thermochromism shifts were detected. The turn-off-on halochromism phenomena were observed in the acidic and basic medium. On the other hand, the fluorescence of the free SB ligand was turned off via complexation to the Cu(II) center. In the presence of H2O2 as green oxidant and under mild oxidation catalytic condition, the three complexes successfully catalyzed the formation benzaldehyde from benzyl alcohol

Crystal structure and spectral of new hydrazine-pyran-dione derivative: DFT enol↔hydrazone tautomerization via zwitterionic intermediate, hirshfeld analysis and optical activity studies

A novel functionalized Schiff base derivative, (E)-3-(1-(2-(9H-fluoren-9-ylidene)hydrazineyl)ethylidene)-6-methyl-2H-pyran-2,4(3H)-dione, was synthesized via subsequent condensation/tautomerization processes in a high yield. The product was fully characterized using NMR, FT-IR, and single-crystal XRD; the results of DFT simulations were in respectable agreement with crystallographic data. To elucidate the isomerization, the enol↔hydrazinium tautomerism has been pursued theoretically, suggesting an intramolecular single proton transfer (SPT) from enol (O ….H) to the closest NC unit, giving the hydrazine (N–H) via [N+—H ….O−] S (6) zwitterionic intermediate. The results of Hirshfeld surface analysis (HSA) and Molecular electronic potential (MEP) were matching the experimental XRD results. Since a number of hydrogen bonding groups, C–H …. π, and π …. π-stacking interactions were detected experimentally. The optical properties of the desired compound were experimentally and theoretically figure out.The authors acknowledge the Algerian Directorate General for Scientific Research and Technological Development and the Algerian Ministry of Higher Education and Scientific Research, for support of this work. Researchers Supporting Project (RSP-2020/78), King Saud University, Riyadh, Saudi Arabia

Microwave-assisted palladium-catalyzed cross-coupling reactions: Generation of carbon-carbon bond

Cross-coupling reactions furnishing carbon–carbon (C–C) bond is one of the most challenging tasks in organic syntheses. The early developed reaction protocols by Negishi, Heck, Kumada, Sonogashira, Stille, Suzuki, and Hiyama, utilizing palladium or its salts as catalysis have, for decades, attracted and inspired researchers affiliated with academia and industry. Tremendous efforts have been paid to develop and achieve more sustainable reaction conditions, such as the reduction in energy consumption by applying the microwave irradiation technique. Chemical reactions under controlled microwave conditions dramatically reduce the reaction time and therefore resulting in increase in the yield of the desired product by minimizing the formation of side products. In this review, we mainly focus on the recent advances and applications of palladium catalyzed cross-coupling carbon–carbon bond formation under microwave technology

Synthesis, structural elucidation and optical activity of symmetric Schiff base-functionalized ferrocenes: Synergetic experimental and DFT insights

A number of Schiff base functionalized derivatives (3a-c) was synthesized from the conventional dehydration of ferrocenecarboxaldehyde and diamine precursors in acetonitrile as a solvent at ambient conditions. IR, UV–Vis, elemental analysis, 1H- and 13CNMR were used to elucidate the novel bis-Schiff base compounds. The nature of electronic absorptions was tracked using Time-Dependent Density-Functional Theory (TD-DFT). The molecular electrostatic potential illuminated that the target compounds are sharing relatively akin electronic distributions. In order to determine the electrophilic and nucleophilic sites, surface analysis of the structures was examined for this purpose. These sites are expected to possess an indispensable role to stabilize and robust the structures via typical hydrogen bonding and non-classical CH···π interactions. Type and influence of solvents on absorption spectra were pursued for the selected model (3a), in which aprotic solvents showed negative solvatochromism (more stable ground state), whereas protic solvents delivered positive solvatochromism (more stable excited state). For example, the metal-to-ligand charge transfer band displayed a gradual shift of the λmax (12 nm) when the type of solvent was switched from polar aprotic (ethyl acetate) to polar protic (methanol) due to the formation of hydrogen bonding, causing bathochromic shift. Eventually, the computationally resulting energy gap of the new products (ΔE) were found to be −4.258 (3a), −4.022 (3b) and −3.105 (3c) eV. These values were compared and found to be in a close level with produced figures from the spectra of density of states and with experimentally determined values using Tauc approach.Qatar National Research Fund: UREP28-036-1-00

XRD/HSA, noncovalent interactions and influence of solvent polarity on spectral properties of dithiocarbazate schiff base and its cis-Cu(II) complex: Experimental and theoretical studies

A N,S-bidentate ligand (LH) was synthesized via the condensation of S-benzyldithiocarbazate with acetophenone. The produced Schiff base ligand was reacted with a copper(II) salt to yield a neutral cis-Cu(II) complex. The influence of solvent polarity on spectral properties were demonstrated for the new complex in different organic solvents. The global reactivity parameters were estimated by means of energy values of the frontier molecular orbitals. Both the desired LH and its complex have been characterized by XRD-crystal analysis. In solid state the LH exists in a thione tautomeric form, while the deprotonated form of is chelated to the Cu(II) center through neutral nitrogen of azomethine and ionic sulfur of thiol, giving rise to tetrahedrally distorted square planar geometry around the metal center, in which the two ligands coordinated in cis-configuration. The noncovalent interactions were evaluated via Hirshfeld surface analysis (HSA), reflecting the presence of four position of short contacts for both the free ligand and its complex. Moreover, the formation of hydrogen bonds of the types NH⸱⸱⸱S=C and CH⸱⸱⸱S=C were observed in the ligand structure, while H⸱⸱⸱Caromatic interactions were perceived in both structures of the ligand and complex, approved by the XRD-packing results

Synthesis of Novel Aqua ƞ4-NNNO/Cu(II) Complexes as Rapid and Selective Oxidative Catalysts for O-Catechol: Fluorescence, Spectral, Chromotropism and Thermal Analyses

A new tetradentate Schiff base (SB), (E)-4-fluoro-2-(1-((2-(piperazin-1-yl)ethyl)imino)ethyl)phe-nol, was synthesized from condensation of 2-(1-piperazinyl)ethylamine and 5-fluoro-2-hydroxyacetophe-none. This ligand was coordinated with three copper(II) salts (CuCl2, CuBr2 and Cu(NO3)2·3H2 O) separately, giving rise to new neutral water-soluble Cu(II)/η4-NNNO complexes (1–3). The new materials were fully characterized by standard spectroscopic, elemental, thermal, electronic, absorption, and fluorescence analyses. The chromotropism investigation of the aqueous solutions of the complexes revealed notable outcomes. A turn off-on halochromism effect was observed, both in the acidic and basic mediums. The green-colored solution was changed to colorless (off) upon the addition of HCl, while the initial green color was reversibly restored (on) after the addition of NaOH. On the other hand, bathochromic solvatochromism shifts were noticed in various solvents. Interestingly, complex 2 displayed a remarkable blue fluorescence shift (∆λ = 90 nm) when compared to its SB ligand. The oxidation capability of the three complexes was successfully demonstrated for the conversion of o-catechol to o-benzoquinone in aqueous solutions and in the presence of H2 O2, an environmentally friendly oxidant, under mild reaction conditions

Synthesis, physicochemical, thermal, and XRD/HSA interactions of mixed [Cu(Bipy)(Dipn)](X)2 complexes: DNA binding and molecular docking evaluation

Two water-soluble dicationic complexes, [Cu(bipy)(dipn)](BF4)2 (1) and [Cu(bipy)(dipn)](NO3)2 (2) (bipy = 2.2-bipyridine and dipn = dipropylenetriamine), were synthesized in high yields. The desired complexes were characterized by CHN-EA, UV–Vis, SEM, EDS, FT-IR, TGA, and XRD. The single-crystal XRD of [Cu(bipy)(dipn)](BF4)2 reflected that Cu(II) complex is formed in a distorted square pyramid configuration. The Hirshfeld surface analysis (HSA) confirmed more powerful atom–atom interaction, the hydrogen bonding in H…F, supporting the outcome of XRD. The influences of the CT-DNA/complexes were gathered by viscosity, CV, and electronic absorption measurements. The estimated binding constants (Kb) for 1 and 2 were 4.5 × 104 and 3.4 × 104 M−1, respectively. Complex 2 revealed slightly poorer DNA binding capability than 1. Eventually, the molecular docking of [Cu(bipy)(dipn)]+2 species was evaluated and demonstrated employing 1BNA-DNA segment.The authors appreciate the Deanship of Scientific Research at King Saud University for funding this research work through grant # RG-1440-141

Indacenodithiazole-Ladder-Type Bridged Di(thiophene)-Difluoro-Benzothiadiazole-Conjugated Copolymers as Ambipolar Organic Field-Effect Transistors

A series of four donor-acceptor conjugated copolymers P1-P4 with linear and branched side chains based on a ladder-type indacenodithiazole (IDTz) moiety containing an electron-deficient thiazole unit are copolymerized with di-2-thienyl-2,1,3-benzothiadiazole (DTBT) and 4,7-di(thien-2-yl)-5,6-difluoro-2,1,3-benzothiadiazole (DTBTff) as building blocks. Their optical, electrochemical, and thermal properties and charge transport behavior in organic field-effect transistors (OFETs) are studied. All copolymers exhibit nearly identical features in solution with good solubility. In the solid state, P1 does not exhibit a significant shift, while P3 shows a 27 nm red shift, thus illustrating the influence of the side chain. In the case of copolymers P1 and P2 having linear side chains, there is a clear effect of fluorination on the film morphology, while it is less pronounced in the case of polymers P3 and P4 having branched side chains. All copolymers P1-P4 have similar highest occupied molecular orbitals regardless of fluorination, while fluorinated polymers P2 and P4 result in an increase in the lowest unoccupied molecular orbital. In addition, density functional theory calculations reveal that the energy levels of IDTz are down-shifted in comparison to its IDT counterpart containing an electron-rich thiophene unit. OFETs based on all copolymers exhibit ambipolar behavior; among the four copolymers, P2 having a linear dodecyl side chain exhibits remarkable transport properties with saturated hole mobility as high as 0.87 cm2 V-1 s-1, while P3 exhibits the highest electron mobility of up to 0.50 cm2 V-1 s-1. Our results set an interesting path to further utilize the electron-deficient thiazole block in semiconducting materials