Proton Transfer Salt Research Articles

Aniline-2,5-disulfonic acid based new proton transfer salt and new Co(II) and Cu(II) coordination polymers: synthesis, structural and antimicrobial studies

Aniline-2,5-disulfonic acid based new proton transfer salt and new Co(II) and Cu(II) coordination polymers: synthesis, structural and antimicrobial studies

ANTIMICROBIAL ACTIVITY OF PROTON SALTS OF 3-(SULFAMOYLPHENYLCARBAMOYL)ACRYLIC ACID DERIVATIVES WITH AMINOPYRIDINE DERIVATIVES

Ten proton transfer salts (9-18) were synthesized from the reaction of 2-aminopyridine (1), 2-amino-3/4/5/6-methylpyridines (2-5) and 3-aminomethylpyridine (6) with (E)-3-(3/4-sulfamoylphenylcarbamoyl)acrylic acid (7 and 8), respectively. Bacillus subtilis (wild culture), Candida albicans (ATCC 14053) (yeast), Enterococcus faecalis (ATCC 29212) (Gram positive), Escherichia coli (ATCC 25922), Listeria monocytogenes (ATCC 7644), Pseudomonas aeruginosa (ATCC 27853), Staphylococcus aureus (NRRL B-767) (Gram negative) bacterial microorganisms have been tested against the antimicrobial evaluation of compounds (1–18). Vancomycin, Cefepime, Levofloxacin and the antifungal substance Fluconazole were used as antibacterial reference compounds for comparing the MIC values of 1-18. Compounds 1, 3-6, 8-13, 15, 17 and 18 for E. faecalis, 5 for B. subtilis, 1, 3-12, 15, 17 and 18 for S. aureus, 3, 9, 10, 13, 15 and 17 for L. monocytogenes, 16 for E. Coli and 4 for P. aeruginosa the best effect are observed. Proton transfer salts {9, 14, 15 and 17} were showed higher effect than Fluconazole while other compounds (except compounds 2 and 4) had similar effects with Fluconazole. The compounds 2 and 4 showed less activity than Fluconazole.

Carbonic anhydrase inhibitory activities of novel proton transfer salts and their Cu(II) complexes

In this study, two new proton transfer salts of sulfonamide derivatives of maleic acid, namely (ClHabt)+(mabsmal)– (1) and (ClHabt)+(pabsmal)– (2), were obtained from 2-amino-6-chlorobenzo­thiazole (Clabt) and N-(3-sulfamoylphenyl)maleamide acid (Hmabsmal) and N-(4-sulfamoyl­phenyl)maleamide acid (Hpabsmal), respectively. Also, the Cu(II) complexes (3 and 4) of salts (1 and 2) and of Hmabsmal (5) were prepared. Compounds 1‒5 were characterized by elemental, NMR (1H and 13C), FTIR, and thermal analyses, as well as UV-Vis, magnetic moment, and molar conductivity measurements. Carbonic anhydrase isoenzymes (hCA I and II) were purified from human erythrocyte cells by affinity chromatography. The effects of the synthesized compounds on the hydratase and esterase activities of CA isoenzymes were studied in vitro. The results reveal that the synthesized compounds inhibit both esterase and hydratase activities of hCA I and hCA II. The inhibition constants of the compounds (Ki) were determined according to the esterase activity measurements. Ki values of 1‒5 are in the range of 0.06 ± 0.003 µM and 4.25 ± 0.100 µM for hCA I, and of 0.02 ± 0.001 µM and 3.21 ± 0.200 µM for hCA II.

Proton-transfer salts of diphenylphosphinic acid with substituted 2-aminopyridine: crystal structure, spectroscopic and DFT studies.

Three proton-transfer salts of diphenylphosphinic acid (DPPA) with 2-amino-5-(X)-pyridine (AMPY, X= Cl, CN or CH3), namely, 2-amino-5-chloropyridinium diphenylphosphinate, C5H6ClN2+·C12H10O2P- (1, X= Cl), 2-amino-5-cyanopyridinium diphenylphosphinate, C6H6N3+·C12H10O2P- (2, X= CN), and 2-amino-5-methylpyridinium diphenylphosphinate, C6H9N2+·C12H10O2P- (3, X= CH3), have been synthesized and characterized by FT-IR and 1H NMR spectroscopy, and X-ray crystallography. The crystal structures of compounds 1-3 were determined in the space group P\overline{1} for 1 and 2, and C2/c for 3. All three compounds contain N-H...O hydrogen-bonding interactions due to proton transfer from the O=P-OH group of DPPA as donor to the pyridine N atom of AMPY as acceptor. The proton transfer of compounds 1-3 was also verified by 1H NMR and FT-IR spectroscopy. The stoichiometry of all three proton-transfer salts was determined to be 1:1 and the Benesi-Hildebrand equation was applied to determine the formation constant (KCT) and the molar extinction coefficient (ϵCT) in each case. Theoretical density functional theory (DFT) calculations were performed to investigate the optimized geometries, the molecular electrostatic potentials (MEP) and the highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO) of all three proton-transfer salts. The results showed good agreement between the experimental data and the DFT computational analysis.

A Short Review on Structural Concepts of Metal Complexes of Proton Transfer Salts of Pyridine-2-Carboxylic Acid

In this study, a brief review of the proton transfer salts synthesized from the reaction of piperazine with pyridine-2-carboxylic acid and their metal complexes since 2009 was made. The metals in the studied compounds are mostly d-block metals. In complexes, the anionic component of the salt is coordinated to the metal, while the cationic component is present only as a complementary ion in a complex.

Synthesis, characterization, biological and dielectric studies of a proton transfer compound of pyridine-2,6-dicarboxylic acid with 1H-benzimidazole-2-amine and its vanadium and iron complexes

A proton transfer salt, (HBIA+)(HPDA−)·H2O (L), and its vanadium (HBIA)[VO2(PDA)] (C1) and iron complexes, (HBIA)[Fe(PDA)2]·2H2O (C2) [H2PDA = pyridine-2,6-dicarboxylic acid; BIA = 1H-benzimidazole-2-amine] have been synthesized and characterized by elemental analysis, FT-IR, UV–Visible, 1H and 13C NMR and single crystal X-ray diffraction (SC-XRD) studies. According to SC-XRD, compound L and C2 crystalizes in Monoclinic (P21/c) and C1 in Triclinic (P-1) crystal system and exist as multi-component proton transfer systems stabilized by COO−NH+ ion pair interactions. Thermal, biological and material aspects of compounds were explored by TG-DTA study, antimicrobial, antidiabetic and dielectric study. Antibacterial activity was evaluated against the microorganisms, Escherichia coli (ATCC 25,922), Staphylococcus aureus (ATCC 25,923), Pseudomonas aeroginosa (ATCC 2783), Streptococcus mutans (MTCC 890) and Klebsiella pneumonia (ATCC 13,883). Antifungal activity was evaluated against Aspergillus niger (ATCC16404) and Candida albicans (ATCC 10,231). Band gap energy values with UV–Visible spectra reveal the semiconducting nature of compounds. The vanadium complex shows significant antidiabetic activity (IC50value = 315 µg/mL) compared with the standard reference. Presence of easily polarizable water molecule is responsible for the high dielectric constant value (ԑ = 41.96 at 1 Hz) and ac conductivity (σac) for the iron complex C2.

Amorphous Drug-Polymer Salts: Maximizing Proton Transfer to Enhance Stability and Release.

An amorphous drug-polymer salt (ADPS) can be remarkably stable against crystallization at high temperature and humidity (e.g., 40°C/75% RH) and provide fast release. Here, we report that process conditions strongly influence the degree of proton transfer (salt formation) between a drug and a polymer and in turn the product's stability and release. For lumefantrine (LMF) formulated with poly(acrylic acid) (PAA), we first show that the amorphous materials prepared by slurry conversion and antisolvent precipitation produce a single trend in which the degree of drug protonation increases with PAA concentration from 0% for pure LMF to ∼100% above 70 wt % PAA, independent of PAA's molecular weight (1.8, 450, and 4000 kg/mol). This profile describes the equilibrium for salt formation and can be modeled as a chemical equilibrium in which the basic molecules compete for the acidic groups on the polymer chain. Relative to this equilibrium, the literature methods of hot-melt extrusion (HME) and rotary evaporation (RE) reached much lower degrees of salt formation. For example, at 40 wt % drug loading, HME reached 5% salt formation and RE 15%, both well below the equilibrium value of 85%. This is noteworthy given the common use of HME and RE in manufacturing amorphous formulations, indicating a need for careful control of process conditions to ensure the full interaction between the drug and the polymer. This need arises due to the low mobility of macromolecules and the mutual hindrance of adjacent reaction sites. We find that a high degree of salt formation enhances drug stability and release. For example, at 50% drug loading, an HME-like formulation with 19% salt formation crystallized faster and released only 20% of the drug relative to a slurry-prepared formulation with 70% salt formation. Based on this work, we recommend slurry conversion as the method for preparing ADPS for its ability to enhance salt formation and continuously adjust drug loading. While this work focused on salt formation, the impact of process conditions on the molecular-level interactions between a drug and a polymer is likely a general issue for amorphous solid dispersions, with consequences on product stability and drug release.

The syntheses, structural and biological studies of Co(II) complexes of 1,2-Bis(pyridin-4-yl)ethane with 2-aminobenzene-1,4-disulfonic acid and 2,6-pyridinedicarboxylic acid

The newly synthesized salt named 4,4′-(ethane-1,2-diyl)bis(pyridin-1-ium) 2-aminobenzene-1,4-disulfonate, (H2BPE)2+(ADSA)2− (1), was prepared from the reaction of 1,2–bis(pyridin–4–yl)ethane (BPE) and 2–amino-benzene–1,4–disulfonic acid (H2ADSA). Two new metal complexes of 4,4′-(ethane-1,2-diyl)bis(pyridin-1-ium) 2-aminobenzene-1,4-disulfonate were also synthesized: The first complex [Co(BPE)2(H2O)4](ADSA).BPE (2) has been synthesized from the obtained proton transfer salt (1). The second complex, {[Co(BPE)(H2O)4]}n[Co(DPC)2].2H2O (4), is a one–dimensional coordination polymer and was synthesized using proton transfer salt (H2BPE)2+(DPC)2- (3). Elemental analysis, Nuclear Magnetic Resonance, Infrared and Ultraviolet–Visible spectra methods were used to elucidate the structure of 1. Elemental analysis, magnetic moment measurements, spectral (UV–Vis, AAS and IR) and X–ray crystallographic analysis were applied for structural manalysis of 2 and 4. X–ray crystallographic study for 2 and 4 revealed that in both complexes the BPE coordinated the Co(II). In compound 2, the coordination periphery of the Co(II) consists of two nitrogens from two BPE, four oxygens from four H2O molecules and forms the six–coordinated octahedral geometry. X–ray crystallographic analysis of 4 showed that the complex was polymer and the metal ions were linked by BPE ligand bridges. The molecular structure of coordination polymer 4 contains both cationic and anionic complexes, each with an octahedral geometry. The coordination sphere of the cationic complex consists of two nitrogens of two BPE and four oxygens of four aqua molecules. On the other hand, the two DPC2− ligands contribute two nitrogens and four oxygens to the coordination sphere of the anionic complex. The antibacterial and antifungal capabilities of the produced compounds were further investigated, and the MIC (Minimum Inhibitory Concentration) values were compared to those of related control substances.

The new salt of 2-amino-3-methylpyridine with dipicolinic acid and its metal complexes: Synthesis, characterization and antimicrobial activity studies

A new proton transfer salt (3) synthesized from 2-amino-3-methyl pyridine with dipicolinic acid and its Fe(III) (4), Co(II) (5), Ni(II) and two Cu(II) (7 and 8) complexes were synthesized and characterized by NMR (1H and 13C), AAS, FT-IR, magnetic measurement, molar conductivity and UV. X–ray crystallography was performed to illuminate the structure of compounds 6 and 8. Additionally, metal salts (9–12), free compounds (1 and 2), simple metal complexes (13–20) of compounds 1 and 2 and synthesized compounds (3–8) have been assayed for their antimicrobial activities against Escherichia coli (ATCC 25,922) (Gram negative), Enterococcus faecalis (ATCC 29212) (Gram positive), Staphylococcus aureus (ATCC 29213) (Gram positive), Candida parapisilosis (ATCC 22019) (yeast), Candida albicans (ATCC 14053) (yeast) and Candida krusei (ATCC 6258) (yeast). Results of analyses were compared with Cefepime, Vancomycin and Levofloxacin (standard antibacterial agents) and Fluconazole (standard antifungal agents). Compounds with the best activity are 1, 3, 11, 16 and 17 (62.50) for E. Coli, 1, 11, 13 and 17 (31.25) for S. aureus, 11, 17 and 18 (31.25) for E. faecalis, 1, 3, 16 and 17 (31.25) for C. parapsilosis, 1 (15.60) for C. albicans and 1, 17, 18 and 20 (31.25) for C. krusei. Against all bacteria and yeasts, compound 17 had the highest activity (32.25) (except for C. albicans).

Synthesis and Characterization of Proton Transfer Salts of 2-Aminobenzothiazole Derivatives

Özet
 Bu çalışmada, önce (E)-4-okso-4-(3-sülfamoyilfenil)amino)büt-2-enoik asit (Habsmal), maleik anhidrit (mal) ile 3-aminobenzensulfonamit’in (abs) tepkimesinden elde edilmiştir. Daha sonra Habsmal ile 2-aminobenzotiyazol (abt) (1) ve 2-amino-6-etoksibenzotiyazol’ün (EtOabt) (2) tuzları sentezlenmiştir. Ayrıca 5-sülfosalisilik asit (H3ssa) ile 2-amino-6-hidroksobenzotiyazol (HOabt) (3) ve 2-amino-6-nitrobenzotiyazol’ün (NO2abt) (4) tepkimelerinden proton transfer tuzları elde edilmiştir. Amorf halde elde proton transfer tuzlarının yapıları, elementel analiz, NMR (1H ve 13C), FT-IR, yük denkliği ve daha önceki çalışmalar ile önerilmiştir. Bu analiz sonuçlarına göre asit ve baz birleşme oranları 1:1 olarak bulunmuştur.

Two new Cu(II) coordination complexes with 1,2-bis(pyridin-4-yl)ethane bridge-ligand: Synthesis, characterization and antimicrobial activity

From the reaction of pyridine-2,6-dicarboxylic acid (H2PDC) with 1,2-bis(pyridine-4-yl)ethane (BPE), a new proton transfer salt, 4,4′-(ethane-1,2-di-yl)bis(pyridin-1-ium) pyridine-2,6-dicarboxylate (H2BPE)2+(PDC)2- (1), has been obtained. Two copper complexes, [Cu6(PDC)6(BPE)3(H2O)4].3H2O (2) and [Cu2(PDC)2(BPE)(H2O)2].H2O (3), were also synthesized. The first one was obtained from the proton transfer salt at room temperature, and the second one was obtained with mixed-ligand under hydrothermal conditions. Spectral (1H, 13C NMR, FT–IR and UV–VIS) and elemental analysis were performed for the structural analysis of the proton transfer salt. In order to determine the structures of the complexes, X-ray crystallography, spectral (AAS, UV–VIS and FT–IR), magnetic moment measurements and elemental analyses were carried out. Except for the Cu1 and Cu1i centers, which have a distorted square-planar geometry in 2, single-crystal X-ray analyzes of 2 and 3 revealed that the copper centers (Cu2-Cu2i and Cu3-Cu3i for 2 and Cu1-Cu1i for 3) are five-coordinated and have a distorted square-pyramidal geometry. Antimicrobial evaluation of compounds (1–3) has been tested against Bacillus subtilis, Listeria monocytogenes (ATCC 7644), Enterococcus faecalis (ATCC 29212) (Gram positive), Staphylococcus aureus (NRRL B-767), Escherichia coli (ATCC 25922) (Gram negative), Pseudomonas aeruginosa (ATCC 27853) and Candida albicans (F89) (yeast) microorganisms. The Minimum Inhibitory Concentration (MIC) values of the new 1–3 were compared with the antibacterial reference compounds Levofloxacin Cefepime, Vancomycin and the antifungal compound Fluconazole.

4,4'-(Ethene-1,2-diyl)dipyridinium bis(2-hy-droxy-3-meth-oxy-benzoate).

In the title double proton-transfer salt, C12H12N2 2+·2C8H7O4 -, consisting of a 1:2 ratio of 4,4'-(ethene-1,2-diyl)dipyridinium cations (trans bipyridinium ethyl-ene) to 2-hy-droxy-3-meth-oxy-benzoate anions (o-vanillate), the complete cation is generated by crystallographic inversion symmetry and it is linked to adjacent o-vanillate anions by N-H⋯O hydrogen bonds, forming trimolecular assemblies. The trimers are linked by C-H⋯O hydrogen bonds as well as aromatic π-π stacking inter-actions into a three-dimensional network. The anion features an intra-molecular O-H⋯O hydrogen bond.

Synthesis and characterization of Cu(II) complexes of proton transfer salts derived from piperazine derivatives and 5-sulfosalicylic acid

In this study, proton transfer salts (H2Etpip)(Hssa), (H2HOEtpip)(Hssa) and (HAcpip)(H2ssa), have been obtained by reactions between 1-ethylpiperazine (Etpip), 1-(2-hydroxyethyl)piperazine (HOEtpip) and 1‑acetylpiperazine (Acpip) and 5-sulfosalicylic acid (H3ssa). Also, Cu(II) complexes of proton transfer salts (H2Etpip)[Cu(Hssa)2]·5H2O, (H2HOEtpip)[Cu(Hssa)2]·5H2O and (H2Acpip)[Cu(Hssa)2]·5H2O) have been synthesized. The structures of proton transfer salts have been proposed by using FT-IR, 1H and 13C NMR spectroscopy, and elemental analysis. The structures of the amorphous metal complexes have been proposed by atomic absorption spectrometry, FT-IR, magnetic susceptibility, molar conductivity techniques, and elemental analysis. Antimicrobial activities of compounds have been tested against Staphylococcus aureus (ATCC 29213) (Gram-positive), Escherichia coli (ATCC 25922) (Gram-negative), Candida krusei (ATCC 6258) (yeast), and Candida parapsilosis (ATCC 22019) (yeast) microorganisms. For S. aureus, the minimum inhibitory concentration (MIC) values of the synthesized salts were between 31.25 and 62.50 µg/ml, and 15.60 µg/ml for complexes. The MIC values of salts and complexes for E. coli were in the range 125.00–500.00 µg/ml and 31.25–62.50 µg/ml, respectively. The MIC values of the salts for C. krusei were 62.50 µg/ml, and for the complexes in the range 15.60–31.25 µg/ml. For C. parapsilosis, these values were 31.25 µg/ml for all salts and in the range 15.60–62.50 µg/ml for complexes.

Investigation of the effects of the proton transfer salts of 2-aminopyridine derivatives with 5-sulfosalicylic acid and their Cu(II) complexes on cancer-related carbonic anhydrases: CA IX and CA XII

Six novel proton transfer compounds (15–20) obtained from 5-sulfosalicylic acid (1) and 2-aminopyridine derivatives [2-amino-3-benzyloxypyridine (2), 2-amino-3-hydroxylpyridine (3), 2-amino-3-methylpyridine (4), 2-amino-3-nitropyridine (5), 2-amino-3-nitro-4-methylpyridine (6) and 2-amino-3-nitro-6-methylpyridine (7)] and their Cu(II) complexes (21–26) along with the Cu(II) complexes of 2–7 (9–14) have been prepared and characterized by spectroscopic techniques. The in vitro inhibition effects of all compounds on CA IX and CA XII isozymes as well as on hCA I and hCA II were investigated and the results were compared. The inhibition studies showed that the synthesized compounds are more selective to CA XII isozyme. The hydratase IC50 values of the compounds were determined as in the range of 15.61 ± 2.32 µM–99.02 ± 4.99 µM for hCA I, 22.36 ± 0.75 µM–77.03 ± 4.03 µM for hCA II, 23.90 ± 1.67 µM–138.63 ± 5.45 µM for CA IX, and 9.50 ± 1.16 µM–693.15 ± 8.96 µM for CA XII. The inhibition data have been analyzed using one-way analysis of variance for multiple comparisons (p < 0.0001).

Synthesis, crystal structure, spectroscopic investigations, physicochemical properties of third-order NLO single crystal for optical applications

Abstract A new proton transfer salt, Glyciniun-2-Mesitylenesulphonate (C11H17NO5S) has been synthesized and its corresponding structure was predicted by Single crystal X-ray diffraction. From SCXRD, crystallised in monoclinic crystal system with the space group of P21/c with the unit cell dimensions: a = 13.2546(9) A, b = 10.6363(7) A, c = 9.5362(6) A, V = 1343.98(15) A3, Z = 4. The grown crystal was studied by FTIR, NMR, TG-DTA, CHN analysis, Uv Visible and Z-Scan measurements. The thermal stability was determined by TG/DTA analysis. Vickers microhardness test was carried out to identify the mechanical strength of the material. Third-order non-linear optical response of G2MS crystal was determined by the Z-scan technique.

Antiferroelectric Phase Transition in a Proton-Transfer Salt of Squaric Acid and 2,3-Dimethylpyrazine.

A proton-transfer reaction between squaric acid (H2sq) and 2,3-dimethylpyrazine (2,3-Me2pyz) results in crystallization of a new organic antiferroelectric (AFE), (2,3-Me2pyzH+)(Hsq-)·H2O (1), which possesses a layered structure. The structure of each layer can be described as partitioned into strips lined with methyl groups of the Me2pyzH+ cations and strips featuring extensive hydrogen bonding between the Hsq- anions and water molecules. Variable-temperature dielectric measurements and crystal structures determined through a combination of single-crystal X-ray and neutron diffraction reveal an AFE ordering at 104 K. The phase transition is driven by ordering of protons within the hydrogen-bonded strips. Considering the extent of proton transfer, the paraelectric (PE) state can be formulated as (2,3-Me2pyzH+)2(Hsq23-)(H5O2+), whereas the AFE phase can be described as (2,3-Me2pyzH+)(Hsq-)(H2O). The structural transition caused by the localization of protons results in the change in color from yellow in the PE state to colorless in the AFE state. The occurrence and mechanism of the AFE phase transition have been also confirmed by heat capacity measurements and variable-temperature infrared and Raman spectroscopy. This work demonstrates a potentially promising approach to the design of new electrically ordered materials by engineering molecule-based crystal structures in which hydrogen-bondinginteractions are intentionally partitioned into quasi-one-dimensional regions.

Synthesis, characterization, and pharmacological evaluation of the proton transfer salts of 2-aminobenzothiazole derivatives with 5-sulfosalicylic acid and their Cu(II) complexes

Two proton transfer compounds, formed between 2-aminobenzothiazole derivatives (2-aminobenzothiazole (abt) and 2-amino-6-ethoxybenzothiazole (EtOabt)) and 5-sulfosalicylic acid dihydrate (H3ssa) as parent compounds, (Habt)+(H2ssa)− (1) and (HEtOabt)+(H2ssa)− (2) and their Cu(II) complexes (3 and 4, respectively) have been prepared and characterized using spectroscopic techniques. The single crystal X-ray diffraction method has been also applied to 3 and 4. Although 3 has a distorted octahedral form, 4 exhibits a distorted square pyramidal geometry. All compounds, including saline and diclofenac sodium as standards, have been evaluated pharmacologically for their anti-inflammatory and analgesic activities in rats and mice. Parent compounds (abt, EtOabt, and H3ssa) 3 and 4 show significant anti-inflammatory and analgesic activities as compared with control compounds.

Synthesis and characterization of Cu(II) complexes of 2-amino-6-sulfamoylbenzothiazole and their inhibition studies on carbonic anhydrase isoenzymes

2-Amino-6-sulfamoylbenzothiazole (SMABT) and its proton transfer compound (HSMABT)+(HDPC)− (1) with 2,6-pyridinedicarboxylic acid (H2DPC), and their Cu(II) complexes (2 of SMABT, 3 and 4 of 1) have been prepared and characterized by spectroscopic techniques. Additionally, single crystal X-ray diffraction techniques were applied to all complexes. All compounds, including acetazolamide (AAZ) as the control compound, were also evaluated for their in vitro inhibition effects on human hCA I and hCA II for their hydratase and esterase activities. The synthesized complexes have remarkable inhibitory effects on hCA I and hCA II isoenzymes. The inhibition potentials of the proton transfer salt (1) and the metal complexes (2–4) are comparable with AAZ. Esterase Ki values of the compounds (1–4) are in the range of 0.089 ± 0.008 μM-0.149 ± 0.017 μM for hCA I and 0.046 ± 0.008 μM-0.085 ± 0.019 μM for hCA II. Inhibition data have been analyzed by using a one-way analysis of variance for multiple comparisons (p < 0.0001).

Structural, Spectroscopic Investigation and Computational Study on Nitrate and Hydrogen Oxalate Salts of 2-Aminopyrimidine.

The proton transfer salts of 2-aminopyrimidine with nitric acid (2APNO) and oxalic acid (2APOX) were synthesized and crystallized successfully by solvent evaporation solution growth technique. The crystal packing is stabilized through intricate three dimensional hydrogen bonded network. Both, the molecular structures were optimized with Density Functional Theory (DFT) using B3LYP function and Hartree-Fock method with a 6-311++G(d,p) basis set. Optimized molecular parameters between the methods were compared for the cation showing appreciable agreement. The computed vibrational spectra are compared with experimental result which clearly demonstrates the strong N-H··· O vibrational behaviour. Thermal stability of the crystals were analyzed with TGA/DTA and the melting points of the salts, viz. 2APNO and 2APOX, were identified at 189.5 and 210.9 °C, respectively. The chemical hardness, electronegativity, chemical potential and electrophilicity index of the two crystals were determined by HOMO-LUMO plot. The lower band gap value obtained from the Frontier Molecular Orbital (FMO) analysis favours the possible pharmaceutical/biological activity of the salts.

2-Aminoethanaminium 2-(ethoxycarbonyl)-4,6-dinitrophenolate as a greener route in reducing sugar quantification

3,5-dinitrosalicylic acid (DNS) reducing sugar assay is the most convenient method for quantification of total reducing sugar in biomass hydrolysate, fermentation samples, sugar industry and biotechnology laboratories. The dimeric proton transfer salt 2-aminoethanaminium 2-(ethoxycarbonyl)-4,6-dinitrophenolate (AED) is an intensely colored derivative of DNS and in turn its reduced form intense color showed a superior properties in reducing sugar quantification eliminating phenol and rochelle salt additives using the same practical methodology of DNS giving an overall methodology advantageous than using DNS assay as a greener route.The proton transfer salt has already been X-ray imaged and deposited in Cambridge Crystallographic Data Centre CCDC 1441586 and a comparison was done between DNS and this salt using a salt and sodium hydroxide concentrations as the same as DNS assay as well as the latter phenol-rochelle salt free environment giving correlation coefficient 0.999 and absorptivity nearly two thirds the obtained in case of use DNS assay with added phenol for enhancing absorptivity and rochelle salt for produced color stabilization for the same detection range 0.1-0.5?mg/ml according to Miller procedures. The sensitivity and the reduced form color stability of this proton transfer salt could be interpreted on both of its molecular structure has a double oxidizing groups as well as it has an intense color as compared with DNS and a good reduced form solubility respectively.•DNS in reducing sugar quantification, Miller procedures involving phenol and rochelle salt addition.•AED in reducing sugar quantification as the same detection range as DNS with the elimination of phenol and rochelle salt from the assay.•A greener convenient route in reducing sugar quantification.