Dipyridylamine Research Articles

Efficient and Sustainable Bidentate Amines-Functionalized Resins for Removing Ag+, Cu2+, Pb2+, and Fe3+ from Water.

We evaluate the effectiveness of chelating resins (CR) derived from Merrifield resin (MR) and 1,2-phenylenediamine (PDA), 2,2'-dipyridylamine (DPA), and 2-(aminomethyl)pyridine (AMP) as adsorbent dosimeters for Ag+, Cu2+, Fe3+, and Pb2+ cations from water under competitive and noncompetitive conditions. MR-PDA, MR-DPA, and MR-AMP were obtained in a 95-97% yield and characterized by IR, fluorescence, and SEM. The ability of CRs as adsorbents was determined by batch and flow procedures. MR-PDA showed a batch adsorption capacity order of Fe3+ (29.8 mg/g) > Ag+ (2.7 mg/g) > Pb2+ (2.6 mg/g) at pH 3.4. The flow adsorption showed affinity towards the Ag+ cation at pH 7 (18.4 mg/g) and a reusability of 10 cycles. In MR-DPA, the batch adsorption capacity order was Ag+ (9.1 mg/g) > Pb2+ (8.2 mg/g) > Cu2+ (3.5 mg/g) at pH 5. The flow adsorption showed affinity to the Cu2+ cation at pH 5 (2.2 mg/g) and a reuse of five cycles. In MR-AMP, the batch adsorption capacity was Ag+ (17.1 mg/g) at pH 3.4. The flow adsorption showed affinity to the Fe3+ cation at pH 2 (4.3 mg/g) and a reuse of three cycles. The three synthesized and reusable CRs have potential as adsorbents for Ag+, Cu2+, Fe3+, and Pb2+ cations and showed versatility in metal removal for water treatment.

Lattice-water tweaked Cis-Trans isomerism of a copper(II)-dipyridylamine-azide complex and their aggregation features

This work highlights an interesting study on lattice-water mediated cis-trans isomerism of hydrated mononuclear copper(II) complexes, [Cu(dpa)2(N3)2].xH2O (x = 1,2) containing bidentate chelatant 2,2′-dipyridyl amine (dpa) and co-ligand, azide ion (N3−) and their aggregation characteristics. A variation in the water–methanol (v/v) solvent mixture leads to a successful synthesis of the geometric isomers of the mononuclear hydrated copper(II) complexes. X-ray crystallography evaluates the crucial role of lattice water along with various non-classical forces for the isomeric existence of the copper complexes. Thermal gravimetric analysis, Hirshfeld surface and energy framework analysis attribute the significant contribution of dispersive forces in the formation and preferential isolation of the geometric isomers. Further, the aggregation properties of the geometric isomers have been assessed with spectroscopic characterization attributing an interesting change in the photophysical, structural and morphological features of the molecular aggregates. The facets of the structural and physicochemical properties of the geometrical conformers and their molecular aggregates have also been unveiled.

Interaction of dpyatriz and Cu/Zn-dpyatriz complexes with human telomere DNA: The role of G-quadruplex formation and its effect on antitumor and antitelomerase activity

1,3,5-Triazine derivative of dipyridyl amine (dpyatriz) and the Cu(II), Zn(II) complexes have been prepared, characterized by CHN, IR, NMR and mass measurements and interacted with HTelo8 and HTelo20, the two types of human telomere repeat DNA (TTAGGG)n; n = 8, 20. The telomere DNAs have been treated with all three compounds (dpyatriz, Cu-dpyatriz and Zn-dpyatriz) under parallel/antiparallel and random coiled conditions. The interactions are followed by circular dichrosim measurements, fluorescent intercalator displacement (FID) assays and molecular docking studies through MOE program. The free ligand and its Cu(II) and Zn(II) complexes stabilize predominantly antiparallel G-quadruplex form under antiparallel and no salt conditions. The binding constant (Kb) values calculated for the ligand and complexes are in the range of 1.9 x 105 M-1 to 4.2 x 107 M-1 under various conditions show the higher affinity of G-quadruplex conformations. The FID assay using thiazole orange with HTelo20 clearly depicts the G-quadruplex stabilization through strong binding mode. Also, all the three compounds dpyatriz, Cu-dpyatriz and Zn-dpyatriz show an intercalative mode of interaction with antiparallel G quadruplex DNA in molecular docking studies. The compounds show cytotoxicity with the IC50 values in the range of 50 – 90 nM, and antitelomerase activity in the range of 5 to 10 μM.

Combined experimental and computational studies on the photophysical properties of systematically substituted polypyridyl based ligands on a benzene core

• Investigated dendritic systems show interesting solvent modulated photophysics; • Inter-chromophoric interaction is present in highly substituted systems; • Theoretical calculation results support the experimental observations; • Strongly modulated photochemistry of L1 and L2 in lower DMSO fraction; • Can lead to design new antenna systems with bipyridyl chromophores on benzene core. Photophysical behavior of ligands containing systematically substituted 2,2′-dipyridylamine (DPyA) chromophores on a benzene core was studied by steady-state and time resolved fluorescence experiments in combination with density functional theory (DFT) calculations. All the investigated derivatives show significant solvent modulated photophysical properties. The redshift along with the broadening in fluorescence spectra in polar protic environments could be explained by the formation of extensive solvent hydrogen bonding network with the investigated compounds. On the other hand, extremely low fluorescence yield in aqueous medium is mostly due to the significant drop in radiative deactivation pathway. In addition to the polarity outcome, the contribution of specific interactions like solvent hydrogen bond formation towards the spectral properties were examined by multi-parametric linear regression analysis using Kamlet-Taft (KT) and Catalán formalisms. While the mono and di-substituted systems ( L1 and L2 , respectively) show almost similar excited state deactivation parameters, additional interchromophoric interaction is predicted in the tri-substituted derivative ( L3 ). The experimental results were verified with TDDFT studies on isolated as well as micro-solvated ligand-water complexes.

2,2’-Dipyridylamine: A tripod ligand enabling practical access to diaryl ethers via Cu-catalyzed coupling reaction

2,2’-dipyridylamine (DPA) is hereby firstly reported as a novel and efficient tridentate ligand for promoting copper(I)-catalyzed C-O/S coupling reactions of abundant aryl bromines with related phenols or thiophenols. The key to this very discovery is the identification of an N-donor tripod ligand (DPA), and such a reaction allows the conversion of simple starting materials to complex diaryl ethers or diaryl thioethers, which are important synthetic intermediates in the preparation of bioactive molecules.

A highly sensitive chemosensor for rapid recognition of Cu2+ and HSO3− in 100% aqueous solution

Dual-responsive chemosensors have garnered much research interests owing to the ability of recognizing two analytes simultaneously. Herein, the chemosensor BPIS composed of hemicyanine and 2, 2′-dipyridylamine (DPA) was facilely synthesized for sensitive and expeditious recognition of Cu2+ and HSO3− in 100% aqueous solution. By adding Cu2+, BPIS showed substantial spectral changes accompanied by a noticeable color change from pink to yellow under daylight. The absorbance and fluorescence intensity were linearly correlated to the Cu2+ concentration, enabling the quantitative recognition of Cu2+. The limit of detection (LOD) for Cu2+ was down to 4.02 × 10−9 M. The response time of BPIS towards Cu2+ was 10 s, imparting BPIS great potential in real-time detection of Cu2+. Meanwhile, BPIS manifested ratiometric fluorescence response by introducing HSO3− owing to the 1,4-addition between HSO3− and the unsaturated CC bond of BPIS. The color of the BPIS solution progressively faded from pink to colorless with increasing HSO3− concentration, and a LOD of 3.47 × 10−9 M was obtained. In addition, BPIS-coated test paper was found to be an efficient tool for fast, sensitive, portable detection of Cu2+ and HSO3− by naked eyes. More importantly, the precise detection of Cu2+ and HSO3− in real water and sugars were realized, respectively, by capitalizing on BPIS as the signal tool.

Atomically Precise Preorganization of Open Metal Sites on Gold Nanoclusters with High Catalytic Performance.

Gold nanoclusters with surface open sites are crucial for practical applications in catalysis. We have developed a surface geometric mismatch strategy by using mixed ligands of different type of hindrance. When bulky phosphine Ph3 P and planar dipyridyl amine (Hdpa) are simultaneously used, steric repulsion between the ligands will reduce the ligand coverage of gold clusters. A well-defined access granted gold nanocluster [Au23 (Ph3 P)10 (dpa)2 Cl](SO3 CF3 )2 (Au23 , dpa=dipyridylamido) has been successfully synthesized. Single crystal structural determination reveals that Au23 has eight uncoordinated gold atoms in the shape of a distorted bicapped triangular prism. The accessibility of the exposed Au atoms has been confirmed quantitatively by luminescent titration with 2-naphthalenethiol. This cluster has excellent performance toward selective oxidation of benzyl alcohol to benzaldehyde and demonstrates excellent stability due to the protection of negatively charged multidentate ligand dpa.

Atomically Precise Preorganization of Open Metal Sites on Gold Nanoclusters with High Catalytic Performance

AbstractGold nanoclusters with surface open sites are crucial for practical applications in catalysis. We have developed a surface geometric mismatch strategy by using mixed ligands of different type of hindrance. When bulky phosphine Ph3P and planar dipyridyl amine (Hdpa) are simultaneously used, steric repulsion between the ligands will reduce the ligand coverage of gold clusters. A well‐defined access granted gold nanocluster [Au23(Ph3P)10(dpa)2Cl](SO3CF3)2 (Au23, dpa=dipyridylamido) has been successfully synthesized. Single crystal structural determination reveals that Au23 has eight uncoordinated gold atoms in the shape of a distorted bicapped triangular prism. The accessibility of the exposed Au atoms has been confirmed quantitatively by luminescent titration with 2‐naphthalenethiol. This cluster has excellent performance toward selective oxidation of benzyl alcohol to benzaldehyde and demonstrates excellent stability due to the protection of negatively charged multidentate ligand dpa.

Electrocatalysis of molecular oxygen reduction reaction at liquid-liquid interface and DFT computational study of proton transfer from the conjugate acid of 2,2'-dipyridylamineto oxygen.

In this study, the catalytic effect of 2,2'-dipyridylamine (DPA) on the reduction of oxygen (O2) at the polarized water/1,2-dichloroethane (DCE) interface was investigated. Ferrocene (Fc) and tetrathiafulvalene (TTF) were weak electron donors used in this study. Slow reduction of O2 at the interface containing Fc and TTF was significantly accelerated upon the addition of DPA. Voltammetry and biphasic shake flask experiments revealed that DPA acts as a proton ionophore to transfer protons between the aqueous and organic phases. The PA, GB, and pKa values of all possible conjugate acids of DPA were calculated. Then, a mechanism was suggested to explain the interaction between protonated DPA and oxygen molecular. The mechanism was computationally analyzed by using density functional theory (DFT). Furthermore, DFT calculations at the B3LYP/6-31G** level of theory showed that the conjugate acid species of DPA transfer proton to O2 at the interface. The results show that DPA-H2+ and DPA-H1+ are the best species to transfer proton to molecular oxygen.

Two new pseudo-isomeric nickel (II) metal–organic frameworks with efficient electrocatalytic activity toward methanol oxidation

Searching for non-noble metal catalysts with high activities and low price is critical to the commercialization of methanol oxidation in the process of fuel cells. Herein, two new pseudo-isomeric Ni metal–organic frameworks (Ni-MOFs) (CTGU-17/CTGU-18) have been prepared with 1,4-naphthalenedi-carboxylate (H2NDC), 4,4′-dipyridyl amine (DPA) and Ni(ClO4)2 under hydrothermal condition. Each phase contains one water molecule, but differs dramatically in its bonding to the framework, resulting in different topological networks with fourfold interpenetrating 4-connected dia net (CTGU-17) and (3,7)-connected net (CTGU-18) and diverse electrocatalytic performance for methanol oxidation reaction (MOR). Remarkably, by combining each MOF with the conductive additive, acetylene black (AB), a composite material, AB&CTGU-18(2:4) was confirmed to have an excellent performance for MOR with a high mass specific peak current of 442.3 mA·mg−1. The enhanced electrocatalytic activities and robustness might be attributed to the synergetic effect of acetylene black and the active metal centers of MOFs particles for methanol oxidation. The present work would provide a new insight for the rational design of MOFs-based composites with enhanced methanol oxidation reaction performance.

Synthesis, Characterization, Physicochemical Studies and Antimicrobial Evaluation of Mixed Ligand Complexes Involving Co(II) with 2,2′-Dipyridylamine and Dicarboxylic Acids

In the current research, the complex formation equilibria of 2,2′-dipyridylamine (DPA) with the metal ions Cu(II), Ni(II), Co(II), Mn(II), and Zn(II) are investigated potentiometrically. The relation between the stability constants of the formed complexes and the properties of the central metal ions was investigated. In addition, the solvent effect on the protonation of DPA and Co-DPA complex formation was also investigated and discussed. The formation of the ternary complexes Co(DPA)L (L = some selected dicarboxylic acids) was studied in aqueous solutions at 25 °C and 0.1 mol dm−3 ionic strength. Stability constants and stoichiometry are reported for the complexes formed in solution. The results show that ternary complexes are formed by a simultaneous reaction mechanism. The speciation of all the complexes was resolved. The effect of chelate ring size of the dicarboxylic acid complexes on their stability constants was also examined. The concentration distribution of the complexes in solution was evaluated. The solid complexes [Co(DPA)L] (where L is oxalic, malonic, succinic or 1,1-cyclobutanedicarboxylic (CBDC) acid) have been synthesized and fully characterized with the help of elemental analyses, infrared spectra, magnetic and conductance measurements. Spectroscopic studies and magnetic measurements (Meff) suggest a tetrahedral geometry for Co(II)-complexes. The measured molar conductance values in DMSO indicate that the complexes are nonelectrolytic in nature. The isolated solid complexes have also been screened for their pharmacological activities against some selected bacteria and fungi. The activity data show that the complexes have a significant activity against Escherichia coli (gram negative) and Staphylococcus aureus (gram positive), as well as an antifungal activity against Aspergillus flavus and Candida albicans.

Tridentate bis(2-pyridylmethyl)amine iron catalyst for electrocatalytic proton reduction

For widespread applicability, successful complexes for catalytic hydrogen generation should be inexpensive and easy to synthesize. To this end, a series of tetradentate Fe(III) polypyridyl monophenolate complexes was recently reported that are stable and active electrocatalysts for reducing protons into hydrogen gas. While these complexes were active for hydrogen generation, the ligands were synthesized in moderate to good yield after multiple synthetic steps. Herein we report a tridentate iron dipyridyl amine analogue for hydrogen generation that is synthesized in a single synthetic step from commercially available materials. The resulting complex is an active electrocatalyst operating at −0.95 V vs SHE (−1.57 V vs Fc+/Fc) with a TOF = 16 s−1. The complex is also a precatalyst for photocatalystic hydrogen evolution when paired with fluorescein (chromophore) and triethylamine (sacrificial electron source) in a 1:1 ethanol:water mixture.

Understanding Amyloid-Beta Plaque Formation By Monitoring the Redox Activity of Copper at the Active Site

The Amyloid β peptide (Aβ-42) can be expressed through cleavage of a precursor protein (APP) during post-translational modification as a result of oxidative stress in the brain. Once expressed, the peptide will readily form binding interactions with free metal ions, particularly Cu2+, initiating a series of redox reactions that result in the production of Reactive Oxygen Species (ROS) and amyloid plaques within the brain. This process has been implicated as the major contributing factor in neurodegeneration in Alzheimer’s patients. An increasingly promising area of study in the treatment of AD is to disrupt this pathway using metal ion chelation, which can serve as a form of therapeutic treatment. The work presented herein focuses on different copper coordination compounds and their redox activity using various ligands such as glycine, beta alanine, phenylalanine, 2,2’-bipyridine (bipy), 2,2’-thiodipyridine (DPS), 2,2’-dipyridylamine (DPA), and 1,10-phenanthroline-2-thiopyridine (TPP). Utilizing Cyclic Voltammetry to monitor redox activity, the more stable ligand complexes resulted in a more quasi-reversible cyclic voltammogram, allowing for potential redox cycling between Cu2+ and Cu+ at the Aβ-42 active site. The CV results correlated well with hydroxyl radical trapping experiments that measured the rate of hydroxyl radical production in each complex, and a relationship between redox activity and hydroxyl radical production was observed. With the Aβ-42 peptide, these coordination complexes were analyzed using Atomic Force Microscopy (AFM) to correlate the rate of fibril formation to plaque formation. These results provide valuable insight into ligand design characteristics important for the development of potential therapeutic treatments that slow AD progression.

A porphyrin-based fluorescent probe for optical detection of toxic Cd2+ ion in aqueous solution and living cells

A porphyrin-based water-soluble fluorescent probe was reported for ratiometric detection of cadmium ion (Cd2+) in aqueous solution. This probe bearing two 2,2′-dipyridylamine (DPA) groups as metal chelating moieties which show chelation-produced ratiometric fluorescence effect with Cd2+via the interruption of intramolecular charge transfer (ICT) process. Exhibiting a large ratiometric fluorescence signal, the probe shows high sensitivity, high selectivity as well as quick response when detecting Cd2+ in the physiological pH window with a detection limit of part per billion (ppb) level. Moreover, it displays very low cytotoxicity and can be employed to visualize intracellular Cd2+ in living cells by utilizing laser scanning confocal microscopy.

Simultaneous enhancements of solubility and dissolution rate of poorly water-soluble febuxostat via salts

Novel crystalline forms of febuxostat (HFEB) salts were synthesized by liquid-assisted cogrinding with 2-methylimidazole (2MI) and di-2-pyridylamine (DPA) and characterized by Hirshfeld surface analysis, IR, 1H NMR, single crystal and powder X-ray diffractions, TGA and DSC. Two new HFEB salts featured different stoichiometries: 2:1 molecular ratio in HFEB-2MI and 1:1 molecular ratio in HFEB-DPA. For HFEB-2MI salt, two HFEB molecules lost one proton forming a singly charged hydrogen carboxylate anion H(FEB)2−, which interacted with the disordered 2MI cation via the N3H3A⋯O1i (i: −x, −y, −z+1) and N4H4B⋯O1ii (ii: x, y+1, z−1) hydrogen bonds to form one-dimensional structure. For HFEB-DPA salt, one proton transferred from one HFEB to DPA, which were further connected by N4H1⋯O1 and N3H2⋯O2 hydrogen bonds to form an R22(8) ring motif. HFEB-2MI and HFEB-DPA salts exhibited increased equilibrium solubilities and intrinsic dissolution rates compared to those of HFEB in aqueous medium.

Bipolar host materials with carbazole and dipyridylamine groups showing high triplet energy for blue phosphorescent organic light emitting diodes

A series of new bipolar host materials with carbazole and different number of dipyridyl amine groups were synthesized for blue phosphorescent organic light-emitting diodes (PHOLEDs). Especially, we applied dipyridyl amine to control the polarity as well as electron transporting property of the carbazole based host materials for comparison with the properties of 1,3-di(9H-carbazol-9-yl)benzene (mCP). As a result, all the carbazole based host materials with dipyridyl amine moieties showed very high triplet energies (>2.9 eV) as well as wide band gap (>3.5 eV). Thus, the blue phosphorescent devices employing those materials with bis(4,6-difluorophenyl pyridinato-N,C2)picolinato-iridium (III) (FIrpic) as a dopant and we obtained moderately high external quantum efficiency (EQE) up to 21.6% with N-(3,5-di(9H-carbazol-9-yl)phenyl)-N-(pyridin-2-yl)pyridin-2-amine (DCPPy).

An Insight of the Results Provided by Color‐Tuning Studies Made on Ir(III) Complexes: A pi‐Neutral CF3 Group Viewed by Adjusting Energies of pi‐type Molecular Orbitals

AbstractThe pi‐nature of a CF3 group can be understood through analysis of its bond orbitals (BOs) mixed into the pi‐type molecular orbitals of CF3‐substituted Ir(ppy)2MDPA+ complexes (ppy=2‐phenyl‐pyridine and MDPA=methylated 2,2′‐dipyridyl amine). It has been found that, through this natural bond orbital analysis, the parent’s molecular orbitals (MOs) can be stabilized by χρ*CF BO via negative hyperconjugation and, simultaneously, destabilized by electron lp(F) BO. Since these two competing pi‐effects are virtually counterbalanced as indicated by the vanishing values of crystal orbital overlap populations, the chemical substitution strategy originated from lowering of HOMO by using this electron‐withdrawing CF3 group has been found effective in color‐tuning to blue region. Based on reduced shielding effect due to de‐ creased χρ‐electron density, the reported position dependent CF3‐substitution effects on pi‐type MOs can also be understood through HOMO/LUMO wavefunction analysis.

Synthesis, characterization, crystal structure and solution studies of a novel proton transfer (charge transfer) complex of 2,2′-dipyridylamine with 2,6-pyridine dicarboxylic acid

Reaction between 2,2′-dipyridylamine (DPA) and 2,6-pyridine dicarboxylic acid (dipicolinic acid, dipicH2), in water results in the formation of a proton transfer or charge transfer (CT) complex, (DPAH)+(dipicH)−·H2O, 1. The characterization was performed using 1H NMR and FTIR spectroscopy, elemental analysis and X-ray crystallography. The crystal system is triclinic with space group P1. The structural investigations exhibit that the hydrogen bonds and π–π stacking interactions stabilize the crystal structure of proton transfer complex. The protonation constants of 2,6-pyridine dicarboxylic acid, 2,2′-dipyridylamine and the equilibrium constants for dipic–DPA (1:1) proton transfer system were calculated by potentiometric pH titration method using Hyperquad2008 program. The stoichiometries of the proton transfer species in solution was in agreement with the solid state result.

5,8-Bis[bis(pyridin-2-yl)amino]-1,3,4,6,7,9,9b-heptaazaphenalen-2(1H)-one dimethyl sulfoxide monosolvate dihydrate

In the asymmetric unit of the title compound, C26H17N13O·C2H6OS·2H2O, there is one independent hepta­zine-based main mol­ecule, one dimethyl sulfoxide mol­ecule and two water mol­ecules as solvents. The tri-s-triazine unit is substituted with two dipyridyl amine moieties and a carbonylic O atom. As indicated by the bond lengths in this acid unit of the hepta­zine derivative [C=O = 1.213 (2) Å, while the adjacent C—N(H) bond = 1.405 (2) Å] it is best described by the keto form. The cyameluric nucleus is close to planar (r.m.s. deviation = 0.061 Å) and the pyridine rings are inclined to its mean plane by dihedral angles varying from 47.47 (5) to 70.22 (5)°. The host and guest mol­ecules are connected via N—H⋯O, O—H⋯O and O—H⋯N hydrogen bonds, forming a four-membered inversion dimer-like arrangement enclosing an R 4 4(24) ring motif. These arrangements stack along [1-10] with a weak π–π inter­action [inter-centroid distance = 3.8721 (12) Å] involving adjacent pyridine rings. There are also C—H⋯N and C—H⋯O hydrogen bonds and C—H⋯π inter­actions present within the host mol­ecule and linking inversion-related mol­ecules, forming a three-dimensional structure.

Cadmium Ions Determination in Sea Food Samples Using Dipyridyl-Functionalized Graphene Nano-sheet

In this work, graphene nano-sheets was modified by dipyridyl amine group and used as a novel sorbent for selective separation and preconcentration of cadmium ions. The sorbent was characterized by infrared spectroscopy, transmission electron microscopy, thermal analysis, and elemental analysis. The application of this sorbent was investigated in determination of cadmium ions in sea food samples by flame atomic absorption spectrometry. The effective parameters on adsorption and desorption of cadmium were optimized. The limit of detection, the relative standard deviation and the recovery of the established method were found to be 0.19 ng mL−1, 1.6 %, and 99.1 %, respectively. The method was validated using various standard reference materials and was applied for cadmium determination in sea food sample.