Bipyridine Molecules Research Articles

Crystal structure of a hydrogen-bonded 2:1 co-crystal of 4-nitrophenol and 4,4′-bipyridine

In the title compound, C10H8N2·2C6H5NO3, 4-nitrophenol and 4,4′-bipyridine crystallized together in a 2:1 ratio in the space group P21/n. There is a hydrogen-bonding interaction between the nitrogen atoms on the 4,4′-bipyridine molecule and the hydrogen atom on the hydroxyl group on the 4-nitrophenol, resulting in trimolecular units. This structure is a polymorph of a previously reported structure [Nayak & Pedireddi (2016). Cryst. Growth Des. 16, 5966–5975], which differs mainly due to a twist in the 4,4′-bipyridine molecule.

Nanoarchitectonics of molecular self assembled monolayers by transition metal ion intercalation for enhancement of molecular junction conductivity.

This research delves into the role of metal ions in enhancing the electronic properties of 5,5'-bis(mercaptomethyl)-2,2'-bipyridine (BPD) self-assembled monolayers (SAMs). It combines experimental techniques and numerical simulations to understand the impact of these ions on the structural, electronic, and transport properties of BPD SAMs. Key findings include the varied bonding preferences of metal ions and their significant role in modifying the electronic structure of BPD molecules, leading to enhanced electron delocalization and migration. The study highlights the potential of metal ions in advancing molecular electronics, particularly in the development of high-performance electronic and energy devices.

Controlling Electron Delocalization in Vanadium‐Based Hybrid Bronzes through Molecular Templation

AbstractWe show that the conductivity of hybrid vanadium bronzes—mixed‐valence organic–inorganic vanadium oxides—can be tuned over six orders of magnitude through judicious choice of molecular component. By systematically varying the steric profile, charge density, and propensity to hydrogen bond across a series of eight diammonium‐based molecules, we engender multiple distinct motifs of V−O connectivity within the two‐dimensional vanadium oxide layers of a family of bulk crystalline hybrid materials. A combination of single‐crystal and powder X‐ray diffraction analysis, variable‐temperature electrical transport measurements, and a range of spectroscopic methods, including UV/Visible diffuse reflectance, X‐ray photoelectron, and electron paramagnetic resonance are employed to probe how vanadium oxide layer topology correlates with electron localization. Specifically, alkylammonium molecules yield hybrids featuring more corrugated layers that contain V−O tetrahedra as well as a higher ratio of corner‐sharing to edge‐sharing polyhedra and that exhibit highly localized electronic behavior, while alkyl bipyridinium molecules yield more regular layers with polyhedral edge‐sharing that show substantially delocalized electronic behavior. This work allows for the development of design principles based on structure–property relationships and brings the charge transport capabilities of hybrid vanadium bronzes to more technologically relevant levels.

Controlling Electron Delocalization in Vanadium-Based Hybrid Bronzes through Molecular Templation.

We show that the conductivity of hybrid vanadium bronzes-mixed-valence organic-inorganic vanadium oxides-can be tuned over six orders of magnitude through judicious choice of molecular component. By systematically varying the steric profile, charge density, and propensity to hydrogen bond across a series of eight diammonium-based molecules, we engender multiple distinct motifs of V-O connectivity within the two-dimensional vanadium oxide layers of a family of bulk crystalline hybrid materials. A combination of single-crystal and powder X-ray diffraction analysis, variable-temperature electrical transport measurements, and a range of spectroscopic methods, including UV/Visible diffuse reflectance, X-ray photoelectron, and electron paramagnetic resonance are employed to probe how vanadium oxide layer topology correlates with electron localization. Specifically, alkylammonium molecules yield hybrids featuring more corrugated layers that contain V-O tetrahedra as well as a higher ratio of corner-sharing to edge-sharing polyhedra and that exhibit highly localized electronic behavior, while alkyl bipyridinium molecules yield more regular layers with polyhedral edge-sharing that show substantially delocalized electronic behavior. This work allows for the development of design principles based on structure-property relationships and brings the charge transport capabilities of hybrid vanadium bronzes to more technologically relevant levels.

Design and fabrication of Cu conical (Spiral+Helical) sculptured thin films and their application in SERS

Cu conical (spiral + helical (spiral (3 turns) + helical (2, 12 and 17 turns)) nanostructures were grown on stainless steel mesh (SSM) and glass microscope slide by glancing angle deposition (GLAD). The SSM substrates were used in surface enhanced Raman spectroscopy (SERS) for detection of 4,4′-Bipyridine (4,4′-Bipy) molecules. This design fulfilled the main electromagnetic mechanisms of enhancement of Raman signals, which are near field coupling and the lightning rod effect. The size of the sculptured nanostructures produced on the SSM substrates matched the wavelength of the laser beam of the Raman spectrometer and satisfied the requirements for the enhancement of the surface Raman spectroscopy of the 4,4′-Bipy molecules. A comparison is made on the morphology of the produced nanostructures on SSM, microscope slide and previously published works on other surfaces with the view to different surfaces with different surface roughness. Field emission scanning electron microscope (FESEM) analysis of the samples clearly revealed the morphology of the designed and fabricated nanostructure as conical (spiral + helical) features on both SSM and glass substrates. Crystal structures and optical spectra of the produced samples obtained using grazing angle incident x-ray diffraction (GIXRD) and Vis-NIR spectroscopy. The SERS results showed that although according to the GIXRD data the coated Cu films were oxidized, good enhancement is obtained. Hence, this can be considered as a favor to the applied fields of these samples. Vis-NIR results showed that as the number of turns of the helical part of the structure increased, the absorption of the spectra increased consistent with the discrete dipole approximation (DDA) results reported in the literature. Surface-enhanced Raman spectroscopy results of this work when compared with the available published data showed higher/comparable enhancement irrespective of the type of material used (e.g., Ag, Au and Mn), 4,4′-Bipy concentration, Bipy substrate shape, the method of fabrication and the excitation wavelength of the Raman spectrometer.

Tunable optical properties of bipyridine dithiol molecules self-assembled on gold substrate

Using density functional theory calculations, we study the effect of intermolecular cross-linking and metal ion inclusion on the electronic and optical properties of 5,5’-bis(mercaptomethyl)-2,2’-bipyridine (BPD) molecules self-assembled on gold substrate. The contribution of the molecules to the density of states of the system near the Fermi level becomes more pronounced after cross-linking due to the delocalization of the electronic states towards the molecules. Consequently, the absorption intensity in the infrared and visible ranges of the spectrum enhances after the cross-linking. The other optical parameters of the system (such as refractive index and reflectivity) is also affected by the cross-linking induced structural changes. Optical properties of self-assembled BPD molecules can further be improved by intercalating metal ions which get encapsulated between the pyridinic units of the molecules and create new absorption sites in the visible and UV ranges of the spectrum. These findings can be useful in tuning optical properties of different materials using molecular self-assembly approach.

Temperature-Dependent Semiconducting Behavior of an Organic Cocrystal Driven by the Stacking Mode of Interaction of a 4,4′-Bipyridine Molecule

Temperature-Dependent Semiconducting Behavior of an Organic Cocrystal Driven by the Stacking Mode of Interaction of a 4,4′-Bipyridine Molecule

Bipyridine Ruthenium(II) Complexes with Halogen-Substituted Salicylates: Synthesis, Crystal Structure, and Biological Activity.

Ruthenium complexes currently represent a perspective subject of investigation in terms of potential anticancer therapeutics. Eight novel octahedral ruthenium(II) complexes are the subject of this article. Complexes contain 2,2'-bipyridine molecules and salicylates as ligands, differing in position and type of halogen substituent. The structure of the complexes was determined via X-ray structural analysis and NMR spectroscopy. All complexes were characterized by spectral methods-FTIR, UV-Vis, ESI-MS. Complexes show sufficient stability in solutions. Therefore, their biological properties were studied. Binding ability to BSA, interaction with DNA, as well as in vitro antiproliferative effects against MCF-7 and U-118MG cell lines were investigated. Several complexes showed anticancer effects against these cell lines.

Configuration-Specific Insight into Single-Molecule Conductance and Noise Data Revealed by the Principal Component Projection Method.

We explore the merits of neural network boosted, principal-component-projection-based, unsupervised data classification in single-molecule break junction measurements, demonstrating that this method identifies highly relevant trace classes according to the well-defined and well-visualized internal correlations of the data set. To this end, we investigate single-molecule structures exhibiting double molecular configurations, exploring the role of the leading principal components in the identification of alternative junction evolution trajectories. We show how the proper principal component projections can be applied to separately analyze the high- or low-conductance molecular configurations, which we exploit in 1/f-type noise measurements on bipyridine molecules. This approach untangles the unclear noise evolution of the entire data set, identifying the coupling of the aromatic ring to the electrodes through the π orbitals in two distinct conductance regions, and its subsequent uncoupling as these configurations are stretched.

Stable tetranuclear copper cage as efficient heterogeneous catalyst for C−C and C−N bond forming reactions

Two tetranuclear copper cages with tubular type, [Cu4(BMBA)4((CH3)2N)2(H2O)2] (1) and [Cu4(BMBA)4(Bipy)(H2O)2] (2), were successfully constructed by the reaction of Cu(NO3)2 with dicarboxylic acid 4,4′-[(ethylazanediyl)bis(methylene)]-bis[(1,1′-biphenyl)-2-carboxylic acid] (H2BMBA) under solvothermal conditions. The complexes 1 and 2 exhibit a similar cage structure, formed by four ligands connecting two binuclear copper paddle-wheel secondary building units (SBUs). Interestingly, the complex 2 was obtained by appropriately binding of 4, 4′-bipyridine (Bipy) molecule on the axial positions of two Cu paddle-wheels inside the cage. For this reason, the complex 2 exhibits excellent stability in some common organic solvents at room temperature and aqueous solutions with a pH of 2 to 12. Upon thermal activation of complex 2, the coordinated water molecules can be removed, and its exposed metal active-sites show Lewis acid character, which can be used an efficient heterogeneous catalysis of Knoevenagel condensation (CC) and Clauson-Kaas (CN) reactions.

A Simple, Fast, and Facile Demonstration of a Photochemical Redox Reaction Using Visible Light

Photochemical reactions are the reactions that are induced by light. Many of these reactions are found in natural processes, including photosynthesis and the formation and decomposition of ozone in the atmosphere. Classroom demonstrations are effective in enhancing students’ learning and retention. Herein, we have developed a simple demonstration of a photochemical redox reaction, which can be performed in a classroom or laboratory setting in schools and universities. This demonstration can be performed in both traditional and active-learning formats. A light-yellow solution containing ferric chloride, 2,2′-bipyridine, and sodium pyruvate, when exposed to visible light, produces a pink color that can be discerned within 3 min. The same reaction mixture kept in the dark does not produce a change in color, indicating that light is essential for this reaction. In the presence of light, pyruvate ions reduce ferric ions to ferrous ions, which then form a complex with 2,2′-bipyridine molecules, resulting in the production of a pink color. The intensity of the pink color increases with time, indicating the accumulation of products. This demonstration is simple, does not require a special source of light, and gives an excellent example of a photochemical redox reaction.

Theoretical study on mechanical evolution process of interface between gold electrode and pyridyl anchor group

Pyridyl-ended molecular junctions show high and low breaking forces successively in formation process and at the same time exhibit intriguing conductance switching behaviors. To understand the forming process of pyridyl-ended molecular junctions, the interaction between 4,4′-bipyridine molecule and gold electrode is studied by the <i>ab initio</i>-based adiabatic simulation method. The processes that the molecule moves away from electrode tip with different contact configurations are simulated, and the molecule-electrode interface evolutions, energy of the molecule-electrode system and the force between molecules and electrode are calculated in the simulations. The numerical results show that during the molecule moving away from the pyramid-shaped electrode, the pyridyl is easy to vertically adsorb on the second gold layer of the electrode tip. In this contact configurations, the tip Au atom deviates from the original position due to the lateral pushing force of the pyridyl. It needs about 1.3–1.5 nN stretching force for the pyridyl breaking from the second gold layer and switching to the tip Au atom, which is evidently larger than the force of 0.8–1.0 nN for the molecule breaking from the tip Au atom. This result is well consistent with the experimental observations, which thus reveals the relationship between the interface structures and the stretching force in the formation process of bipyridyl molecular junction in the experiment. The interaction between 4,4′-bipyridine molecule and plane-shaped gold electrode is very weak. It needs no more than 0.5 nN for the molecule breaking from the plane-shaped gold electrode. However, when the molecule adsorbs on the single Au atom which is adsorbed on the surface of plane-shaped electrode, the molecule can sustain 1.7 nN stretching force. Our study shows that the <i>ab initio</i>-based adiabatic stretching simulation method can not only reveal the geometric evolution process of molecule-electrode systems, but also identify the specific contact configurations between molecule and electrode.

Sustainable nanoporous gold with excellent SERS performances

A low-cost Nanoporous Gold (NPG) has been successfully produced by utilizing the simple method of chemical dealloying. Ribbons of a supersaturated solid solution Au33Fe67 were obtained by rapid solidification using melt-spinning technique. Chemical dealloying of the ribbons was achieved in 1 M HNO3 at 70 °C for varying lengths of time. The as-quenched ribbon and as-dealloyed samples have been structurally and compositionally investigated using XRD, FESEM and EDS techniques. The obtained NPG is homogeneous with tunable ligament size and shape, easy-to-handle and free-standing. NPG has been successfully applied as substrate for Surface-Enhanced Raman Scattering (SERS) using 4,4′-bi-pyridine probe molecule. An impressive enhancement in the SERS effect has been observed. The detection limit is recorded to be as low as 10−15 M. The NPG sample shows great potential as an economical and highly sensitive SERS-active substrate for life science applications and ultrasensitive instrumentation. Catalytic properties have been explored demonstrating a high activity of the material. Most notably, a metastable precursor has been favourably obtained from an immiscible Au–Fe system. Usage of critical raw materials has been avoided. A cost-effective starting material has been used in the form of an Fe-rich precursor by pairing abundant and cheap Fe with Au. Then, an elegant and rapid dealloying procedure makes the overall production of NPG an inexpensive and sustainable process.

Raman enhancement (SERS) of the surface phonon modes of TiO2

We report the first observation of the enhancement of Raman forbidden surface phonon modes (SO) of A2u symmetry in TiO2 nanoparticles on the adsorption of 2,2′-bipyridine and N-719 dye molecules. We identify the observed surface modes in conjunction with HREELS studies and attribute their enhancements to (Herzberg-Teller) vibronic coupling between the charge-transfer and the molecular transitions. We conclude that the vibronic coupling is responsible for the enhancements of the surface modes through intensity borrowing. Furthermore, using SERS selection rules, we examine possible orientations of the molecules relative to the surface confirming the Raman forbidden A2u symmetry of the surface modes.

Structural characterization (XRD, FTIR) and magnetic studies of Cd(II)-Sulfamethoxazole-2,2′-bipyridine: DFT and Hirshfeld Surface Analysis

New cadmium(II) complex have been synthesized by the reaction of nitrogen donor ligand sulfamethoxazole (smtxH: 4-amino-N-(5-methylisoxazol-3-yl)benzenesulfonamide) and nötr ligand 2,2′-bipyridine (bipy). The resulting compound is a neutral [The Cd(smtx)2(bipy)2•H2O] complex. The structure of the metal complex have been elucidated by single-crystal X-ray diffraction. The central Cd(II) ion is coordinated by two monodentate sulfamethoxazole anions together with two bidentate bipy ligand forming the octahedral geometry. The theoretical optimized geometrical parameters is calculated by using the Density Functional Theory (DFT) with the B3LYP method at 6–311G(d,p) bases set. Observed and calculated IR frequencies were found to be agreement. Hirshfeld surface analysis has been performed to study the nature of intermolecular interactions within the crystal structure and the finger- print plots, molecular surface contours. Molecular orbital coefficients were obtained using EPR and UV data. The thermal behavior of compound has been investigated.Cd(II)-smtx-2,2′-bipyridine molecule was synthesized. The complex was characterized by FT-IR, XRD. Molecular orbital coefficients were calculated using data from EPR and UV. With the help of Hirshfeld surface analysis, the intermolecular interactions in the crystal structure were interpreted by reducing them to fingerprint graphics. The TGA curves of compound have been examined. Structural and optical properties of the complex were further analyzed by quantum chemical calculations performed using DFT-TDDFT/B3LYP method in combination with LANL2DZ basis set.

DOUBLE Ge(IV)-Co(ІІ) COMPLEXES WITH 1-HYDROXYETHYLIDENEDIPHOSPHONIC ACID AND 2,2-BIPYRIDINE

The novel developed synthesis methods allowed to obtain three Ge(IV)-Co(II) coordination compounds with 1- hydroxyethylidenediphosphonic acid and 2,2`-bipyridine [{Co(bipy)3}2{Co(bipy)(H2O)4}2][{Ge(μ-OH)(μ-hedp)}6Cl2]∙2H2O (1), [Co(bipy)3]4[{Ge(μ-OH)(μ-hedp)}6Cl2]∙30H2O (2), [Co(bipy)3]3[{Ge(μ-OH)(μ-hedp)}6]⋅20Н2О⋅2CH3COOH (3). Complexes are characterized by the methods of elemental analysis, IR-, Diffuse Reflectance spectroscopy, thermogravimetric analysis. All absorption bands presented in the IR-spectra of compounds 1-3 are highlighted in the Table 2. Absorption bands of the P-O bond are detected at ~1053 and ~970 сm-1, that indicates the presence of the fully deprotonated PO32- groups in the composition of complexes. Furthermore, n(OH), ν(Ge–Ophosph), d(Ge–OH) bands characteristic for all the previously synthesized compounds with [Ge6(m-OH)6(m-hedp)6]6-anion is detected in the IR spectra of 1-3. Presence of the crystal water molecules is confirmed by the ν(OH) at 3400 сm-1. A set of the bands usual for the aromatic molecules (n(C–Harom), n(C–Carom), das(CH3), ds(CH3), n(С–N)) is assigned with 2,2`-bipyridine in the structure of all compounds. A special feature of the IR-spectra of 1 is presence of COOH absorption band at 1700 сm-1, that indicates the location of solvated acetic acid. Complex 1 also contains coordination water molecules, confirmed by the d(H2O) at 1642 сm-1 in its IR-spectrum. Absorption bands of Co–N and Со-О bonds evidence that 2,2`-bipyridine and H2O molecules are coordinated to the cobalt atom. Thermal decomposition of 1-3 differs a lot. Variable interval and temperature of the first endoeffect is explained by the different nature of water in them – crystal (1-3) and coordinated (1). In the diffuse reflection spectra of compounds 1-3, two bands corresponding to the following transitions are observed: 4T1g(F)→ 4T2g (1 – 7250, 2 – 7100, 3 – 7300 сm-1), 4T1g(F)→ 4T1g(P) (1 – 13800, 2 – 14200, 3 – 14000 сm-1). Such results confirm an octahedral configuration of cobalt atom. There was also established, how composition and structure of the synthesized compounds depend from the molar ratio of the reagents and anion of the initial Co(II) salt (chloride, acetate).

Influence of Central-Metallic Atoms of Molecular Junction on Electrical and Thermal Transport

Molecular structures of a series of metal-complexes molecules of bipyrimdine have interesting features in various applications such as industrial and scientific. The transition through metal complexes at molecular structures has a significant role in the metal-bridges interactions. Hence, the bipyrimdine's complex molecules were used to show the effect of the metal atoms on the electronics, electrical, and thermoelectric properties and to identify the π-conjugated system in all attempts before/ or after replaced one carbon with nitrogen atoms in one or two the pyridine rings. SIESTA code, and GOLLUM code programs were used in our calculations. The results showed that the energy gap decreased significantly with the type of metal atoms, which appear in electronic applications at various LUMO-HOMO energy gaps. The electrical and thermal results have confirmed the effect of metal-complexes center atoms in the transmission and Seebeck coefficients. From the position of the Fermi energy (E-EF=0 eV), the conductance and the thermopower values are determined, and thus the specificity figure of merit ZTe was computed. Therefore, we found the ZTe be a high value for bipyridine molecule about 1.7, which is several order of magnitude higher than of the set molecules. Whereas a low value of ZTe for Cr-metal-molecule.

Order beyond a monolayer: The story of two self-assembled 4,4′-bipyridine layers on the Sb(111) | ionic liquid interface

In this study, it has been shown that the ordering of organic molecules is not limited to a highly organised self-assembled monolayer on the electrode's surface. At the interface between semi-metallic Sb(111) electrode and ionic liquid with 4,4′-bipyridine addition, two distinctive stacked adsorbed layers upon each other have been identified by applying in situ scanning tunnelling microscopy and electrochemical impedance spectroscopy methods. The first adlayer in contact with the electrode consists of tightly packed ordered rows. The second adlayer, on top of the first, is characterised by low surface concentration, and its unit cell was obtained experimentally. In addition to experimental data, the likely distribution of 4,4′-bipyridine molecules in the first adlayer has been described using density functional theory calculations combined with machine learning. The gained insights of organic's adsorption from ionic liquids are of fundamental and practical importance in the development of nanoelectronic devices.

Functionalized gold nanoparticles and nanoplatelets synthesized using plant extract and their potential for surface-enhanced Raman spectroscopy

Gold nanoparticles are increasingly used in biomedical fields due to their biocompatibility and their optical properties, such as tunable absorption of light and their efficiency for light to heat conversion, leading to recent developments in applications like photothermal therapy. In this work, gold nanoparticles and nanoplatelets were synthesized using an Aloe Vera leaf extract, without any additional surfactant, and functionalized using 16-mercaptohexadecanoic acid or L-Cysteine. The latest grafted nanoparticles and nanoplatelets were also further functionalized using Alexa Fluor NHS ester, that covalently binds to the amine group of L-Cysteine. They were fully characterized using Scanning/Transmission Electron Microscopy, UV-vis-NIR absorption and Raman spectroscopy The synthesized gold particles possess a large diversity of shapes: platelets with a triangular or hexagonal profile, tetrahedra, decahedra, icosahedra and bipyramids, but also polycrystals made of the assembly of two or three crystals. Their dimensions and proportions are correlated to the plant extract concentration used during the synthesis: the lower the concentration of the plant extract, the bigger the particles. Finally, the particles exhibit localized surface plasmon resonances correlated to their shapes. More, at the vicinity of the functionalized particles, we show that the Raman signal of 2,2’-bipyridine molecules is greatly enhanced, proving their potential use in SERS applications.

Copper(II) complexes based on N-(bis(diethylamino)phosphoryl)-2,2,2-trichloroacetamide with pyridine and 4,4′-bipyridine

Two new Cu(II) complexes, {CuL2⋅(4,4′-bipy)}n (1) and CuL2(Py)2 (2), where bipy = bipyridine; HL = N-(bis(diethylamino)phosphoryl)-2,2,2-trichloroacetamide, representative of carbacylamidophosphate (CAPh) type ligands), have been synthesized and characterized by FTIR and single-crystal X-ray analysis. In both complexes CAPh ligands are coordinated to the copper ions in a bidentate chelate manner through oxygens of the carbonyl and phosphoryl groups. Nitrogen atoms of bipyridine, 1, or pyridine molecules, 2, complete the coordination number of Cu(II) to six. The Cu ions are located in special positions on inversion centers. In the structure of 1, the bipyridine molecules display a bridging function between adjacent copper complexes forming a polymer chain. Phosphoryl and 4,4′-bipy (Py) ligands in both structures are located in trans positions relative to each other.