Complexation Constants Research Articles

Potentiometric Determination of Stability Constants of Binary and Ternary Complexes of L-Tryptophan and Anti-Inflammatory Drugs with Zn(II)

Potentiometric Determination of Stability Constants of Binary and Ternary Complexes of L-Tryptophan and Anti-Inflammatory Drugs with Zn(II)

Embedding of Functionalized Coordination Cages and a Molecular Knot in a Polymeric Membrane for Potentiometric Sensing of Environmentally Important Oxyanions and Halides.

Three kinds of coordination cages and a molecular knot with inductively activated +P-H, N-H, or C-H hydrogen bond donors anchoring in the functionalized cavities were inspected as ionophores to develop polymeric membrane ISEs for potentiometric sensing of environmentally important oxyanions and halides. The proposed ISEs displayed significant preference for perrhenate, phosphate, or chloride with a selectivity pattern distinctively different from the sequence depending on the Gibbs free energy of hydration owing to the high degree of shape, charge, and size selectivity originating from the rigidity and complementarity of the binding cavities. To gain further insight into the response characters of the proposed ISEs, the binding constants of ionophore-anion complexes in the membrane phase were investigated, and the binding affinity, together with the Hofmeister series, correlates well with the determined selectivity pattern of the proposed ISEs. Optimizing the composition of the membrane such as lipophilic additives and plasticizers produced ISEs displaying Nernstian/near-Nernstian potentiometric responses to primary anions with a wide linear range, improved detection limits, good reversibility, and satisfying lifetime. Potentiometric determination of perrhenate, phosphate, and chloride in river water, mineral water, and artificial serum samples was achieved with good recovery and accuracy using the proposed ISEs, demonstrating their potential for real-life applications. These results will shed new light on how novel ionophores could be designed for potentiometric sensing and broaden the scope of host-guest chemistry of coordination cages and molecular knots.

Interaction between pH-shifted ovalbumin and insoluble neohesperidin: Experimental and binding mechanism studies

In this study, ovalbumin (OVA) formed a complex with neohesperidin (NH) via a pH-shifting method. The NH-OVA complex self-assembled into NH-OVA nano-particles, which were then characterized and whose binding mechanism was evaluated by using multi-spectroscopic, thermodynamics, and molecular docking simulation methods. Fluorescence intensity decreased after OVA was complexed with NH. The binding constant of the OVA-NH complex was in the order of 6.32 × 105 M−1 suggesting that the complex is stable. Circular dichroism (CD) analysis showed that α -helix content increased, β-folding, β -turning, and irregular crimp content decreased after OVA and NH binding. Isothermal titration calorimetry results showed that hydrophobic interactions and hydrogen bonds made an important impact in the complex formation. The molecular docking results revealed that Van der Waals forces and hydrogen bonds contributed to the free binding energy of the complex. There were multiple possible surface binding sites between OVA with NH. The obtained results provide new insights into the interaction mechanism of OVA and NH, and as a vehicle for NH, the OVA has shown promising applications in functional foods.

Supplementation of tea polyphenols in sludge Fenton oxidation improves sludge dewaterability and reduces chemicals consumption

The Fenton oxidation improves sludge dewatering but faces notable technical and economic challenges, including a narrow acidic pH range, slow reduction of Fe(III), and the use of high doses of chemicals. Herein, we used a natural polyhydroxyphenol tea polyphenols (TP), as an iron redox conversion enhancer, to mitigate these issues. Compared with the classical Fenton process at pH 3.0, the process with TP (33.8 mg/g dry solids (DS)) improved sludge dewaterability at pH 7.5 in a Fenton-like system with faster Fe(II)/Fe(III) cycling and two times lower consumption of the Fenton reagent. Sludge capillary suction time and specific resistance to filtration decreased from 70 s to 22 s and from 2.7 × 1013 m/kg to 5.2 × 1011 m/kg, respectively, while the required doses of Fe(II) and H2O2 were cut to 25 mg/g DS and 31.2 mg/g DS. Mechanistically, TP could bond readily with Fe(II)/Fe(III) at neutral pH to form stable complexes with complexation constants of 34 ± 161 M−1 and 52 ± 70 M−1, respectively, and reduce part of the Fe(III) to Fe(II) simultaneously. This maintained sufficient soluble Fe in the sludge and boosted efficient conversion of Fe(II)/Fe(III) to yield more hydroxyl radicals (•OH). Subsequently, •OH oxidation resulted in the decomposition of biopolymers with a molecular weight of 108 Da (e.g., 58.2% of polysaccharides and 31.6% of proteins in tightly bound extracellular polymeric substances) into small molecules and disintegration of bioflocs into smaller particles with increased porosity, contact angle, and cell lysis; these changes helped reduce bound water content and improved sludge dewaterability. In addition, the TP-mediated Fenton process disinfected fecal coliforms in the sludge and preserved the sludge organic matters. This work proposes a new paradigm for developing cost-effective sludge dewatering technologies that relies on the synergistic effects of plant polyphenols and advanced oxidation processes.

Separability of stereoisomers by electrokinetic chromatography in presence of a neutral selector – Fundamental aspects assessed by computer simulation

The impact of the two essential parameters, the complexation constant and the mobility of the formed diastereomeric complex, on stereoisomer separation in presence of a neutral chiral selector was assessed by computer simulation for an electrokinetic chromatography configuration with a uniform background electrolyte and one with a cationic discontinues buffer system of isotachophoretic nature. With two enantiomers of norpseudoephedrine as model analytes, data for seven cases featuring complexation in free solution with various combinations of input values, complexation with an immobilized selector and no complexation were analyzed in a hitherto unexplored way. For the uniform buffer study, the determined differences of the effective mobilities and separation selectivities of the stereoisomers were found to be equal to those calculated with the well-known algebraic equations. For the isotachophoretic system with its Kohlrausch adjusted zones, separation is also based on differences in effective mobilities, but the mobility differences cannot be predicted with the same algebraic equation. In both techniques, chiral separations occur due to the presence of the selector and if there is inequality between the mobilities of the transient diastereomeric complexes and the mobility of the free, uncomplexed analyte. Separation of the stereoisomers is possible when complexation constants, complex mobilities or both of these parameters differ. In the isotachophoretic separation a migrating steady-state is formed in which analytes either establish consecutive zones with plateau concentrations or, if present in an insufficient amount, as a peak-like distribution that migrates within a moving steady-state boundary. Simulation data illustrate for the first time the use of a spacer compound that establishes an isotachophoretic zone between enantiomers and thereby provides complete separation of the enantiomers and the possibility of individual detection in peak-mode isotachophoresis. They demonstrate that such an approach could be employed to assess the enantiomeric purity of a chiral compound.

Cocktail of REGN Antibodies Binds More Strongly to SARS-CoV-2 Than Its Components, but the Omicron Variant Reduces Its Neutralizing Ability.

A promising approach to combat Covid-19 infections is the development of effective antiviral antibodies that target the SARS-CoV-2 spike protein. Understanding the structures and molecular mechanisms underlying the binding of antibodies to SARS-CoV-2 can contribute to quickly achieving this goal. Recently, a cocktail of REGN10987 and REGN10933 antibodies was shown to be an excellent candidate for the treatment of Covid-19. Here, using all-atom steered molecular dynamics and coarse-grained umbrella sampling, we examine the interactions of the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein with REGN10987 and REGN10933 separately as well as together. Both computational methods show that REGN10933 binds to RBD more strongly than REGN10987. Importantly, the cocktail binds to RBD (simultaneous binding) more strongly than its components. The dissociation constants of REGN10987-RBD and REGN10933-RBD complexes calculated from the coarse-grained simulations are in good agreement with the experimental data. Thus, REGN10933 is probably a better candidate for treating Covid-19 than REGN10987, although the cocktail appears to neutralize the virus more efficiently than REGN10933 or REGN10987 alone. The association of REGN10987 with RBD is driven by van der Waals interactions, while electrostatic interactions dominate in the case of REGN10933 and the cocktail. We also studied the effectiveness of these antibodies on the two most dangerous variants Delta and Omicron. Consistent with recent experimental reports, our results confirmed that the Omicron variant reduces the neutralizing activity of REGN10933, REGN10987, and REGN10933+REGN10987 with the K417N, N440K, L484A, and Q498R mutations playing a decisive role, while the Delta variant slightly changes their activity.

Chlorination of L-tyrosine and metal complex: degradation kinetics and disinfection by-products generation

The presence of metal ions in drinking water treatment and distribution systems may affect the disinfection process of organic matter, which had aroused people's concern. L-tyrosine can complex with metal ions through carboxyl, carbonyl and amino groups and affected its chemical reactions. In this paper, the complexation of L-tyrosine with common metal ions was studied and the influence of complexation in chlorination with different experimental factors were investigated. It was inferred that L-tyrosine complexed with metal ions by single dentate ligand or double dentate chelation in a ratio of 2:1. The degradation of L-tyrosine-metal complex followed the pseudo-first-order reaction kinetic. TCM, DCAA and TCAA were the main species DBPs in chlorination of L-tyrosine. Compared with L-tyrosine, the reaction rate constants of complex increased by 5.6%, the formation of trihalomethane production decreased by 21.5% and the formation of haloacetic acids production increased by 26.9% at the state of metal complexation. The effect of metal complexation on chlorination was more obvious than that of metal coexistence. For different metal complexation, the order of inhibition on trihalomethane production was Ca2+> Fe3+> Mn2+ and the order of promotion on haloacetic acids production was Mn2+> Fe3+> Ca2+. Moreover, it was found that alkaline conditions were favorable to the formation of DBPs due to the hydroxyl radical. The combination of ultraviolet (UV) and chlorine disinfection promoted L-Tyr degradation and DBPs generation, and the promotion efficiency follow the order: UV/Cl2> UV-Cl2> Cl2.

Enantioseparation of chiral (benzylsulfinyl)benzamide sulfoxides by capillary electrophoresis using cyclodextrins as chiral selectors

Sulfur as a stereogenic center can be found in synthetic compounds and natural products. The current study evaluated the enantioseparation of 16 chiral (benzylsulfinyl)benzamide compounds by capillary electrophoresis using charged cyclodextrins (CDs) as chiral selectors in 50 mM sodium acetate buffer, pH 5.5. The sulfoxides varied in the type and position of the substituent of the benzyl moiety as well as the position and methylation of the amide group. Typically, randomly substituted CDs separated the majority of the model analytes in contrast to single isomer CDs. In case of random substitution, γ-CD derivatives displayed higher resolution ability toward the set of model compounds followed by β-CD and α-CD derivatives. Except for a few examples, the (+)-enantiomer of the analytes migrated before the (–)-isomer irrespective of the type of the CD so that the chiral recognition appeared to be also mostly independent on the structure of the sulfoxides. Evaluation of complexation constants and complex mobilities of selected CD-analyte pairs revealed that the separations were based on the stereoselective complexation by the CD expressed as complexation constants but examples for complex mobilities as the determining factor for the enantiomer migration order were also found. In case of 2-(4-bromobenzylsulfinyl)-N-methyl benzamide in the presence of heptakis(2,3-di-O-methyl-6-O-sulfo)-α-CD reversal of the enantiomer migration order as a function of the CD concentration was observed. Using neutral CD derivatives in the presence of sodium dodecyl sulfate-based micelles at pH 9.0 only few sulfoxides could be enantioseparated.

A BODIPY-based turn-off fluorescent probe for mercury ion detection in solution and on test strips

In this study, a new fluorescence sensor M1 consisting of 4,4-difluoro-4-bora-3a,4a-diazaindacene (BODIPY) and thiosemicarbazide moieties was designed for mercury ion detection. M1 exhibited intense green emission in both solution and solid state. Obvious fluorescence quenching of the solution of M1 in DMF/H2O was observed only in presence of Hg2+ among the metal ions (Hg2+, Li+, Co2+, Cr3+, Mg2+, K+, Mn2+, Al3+, Fe3+, Zn2+, Cu2+, Cd2+, Ag+, Pb2+, Ca2+, Ni2+, Ba2+). The present probe M1 was 1:1 complexed with mercury ion, with complexation constant of 2.98 × 104 M−1. The detection limit of the probe M1 was calculated to be as low as 4.9 × 10−7 M. Moreover, the probe M1 achieved selective and sensitive sensing toward mercury ion on test strips, which guaranteed its potential application.

Complexation thermodynamics of UO22+/diglycolamide complex in a room temperature ionic liquid: A study by optical spectroscopy and microcalorimetry

Complexation thermodynamics of UO22+ and a series of N,N,N’,N’-tetraalkyl diglycolamide (TRDGA) ligands having alkyl chains –CH3 to –C6H13 were investigated in an ionic liquid (IL). The complexation constant for UO22+/DGA complex increased linearly with increasing alkyl chain length of DGA from tetramethyl (logβ1 = 4.52, logβ2 = 8.01) to tetrahexyl (logβ1 = 5.62, logβ2 = 10.3). There were two types of species recorded in the calorimetric titration for all the four ligands, one having endothermic complexation, and other exothermic. This observation was in contrast with those observed for aqueous medium, where both the stepwise complexation enthalpies were endothermic. The structural feature indicated the formation of [UO2L2]2+ type of complex without water or Tf2N− anion in the primary coordination sphere of the uranyl cation.

On the Curcumin and β‐Cyclodextrin Interaction in Aqueous Media. Spectrophotometric and Electrochemical Study

AbstractIt is shown from UV/Vis spectrophotometry measurements, that up to two inclusion complexes between curcumin and β‐cyclodextrin, namely H3Cur(β‐CD) and H3Cur(β‐CD)2, can be formed in aqueous solution at pH=3.6, where the fully protonated and neutral species of curcumin, H3Cur, predominate depending on the β‐CD concentration. The thermodynamic formation constants of these supramolecular complexes were determined and the molar absorptivity coefficients of H3Cur, H3Cur(β‐CD) and H3Cur(β‐CD)2 species were assessed. In the absence of β‐CD, curcumin degradation increases linearly with time at a rate of 3.25 % min−1. However, in its presence, the rate drastically diminishes to 0.11 % min−1. These results were corroborated from independent electrochemical measurements using a bare carbon paste electrode. At 0.01 M β‐CD the first voltammogram cycle displayed single anodic and cathodic peaks while the second cycle is formed by two anodic peaks and one cathodic, all of them being due to single‐electron adsorption‐controlled processes. The current of these peaks can be used to quantify curcumin concentration in real samples.

Study of Interaction of the PARP Family DNA-Dependent Proteins with Nucleosomes Containing DNA Intermediates of the Initial Stages of BER Process.

Reaction of (ADP-ribosyl)ation catalyzed by DNA-dependent proteins of the poly(ADP-ribose)polymerase (PARP) family, PARP1, PARP2, and PARP3, comprises the cellular response to DNA damage. These proteins are involved in the base excision repair (BER) process. Despite the extensive research, it remains unknown how PARPs are involved in the regulation of the BER process and how the roles are distributed between the DNA-dependent members of the PARP family. Here, we investigated the interaction of the PARP's family DNA-dependent proteins with nucleosome core particles containing DNA intermediates of the initial stages of BER. To do that, the nucleosomes containing damage in the vicinity of one of the DNA duplex blunt ends were reconstituted based on the Widom's Clone 603 DNA sequence. Dissociation constants of the PARP complexes with nucleosomes bearing DNA contained uracil (Native), apurine/apyrimidine site (AP site), or a single-nucleotide gap with 5'-dRp fragment (Gap) were determined. It was shown that the affinity of the proteins for the nucleosomes increased in the row: PARP3<<PARP2<PARP1; whereas the affinity of each protein for the certain damage type increased in the row: Native = AP site < Gap for PARP1 and PARP2, Gap<<<Native = AP site for PARP3. The interaction regions of each PARP protein with nucleosome were also determined by sodium borohydride cross-linking and footprinting assay. Based on the obtained and published data, the involvement pattern of the PARP1, PARP2, and PARP3 into the interaction with nucleosome particles containing DNA intermediates of the BER process was discussed.

A near infrared fluorescent probe for detection and bioimaging of zinc ions and hypochlorous acid

It is of great significance to monitor zinc ions (Zn2+) and hypochlorous acid (HClO) conveniently in disease diagnosis and environmental protection. Herein, we successfully prepared a near-infrared fluorescent probe based on dicyanoisophorone derivative and methyl hydrazate by Schiff base reaction for effective detection of Zn2+ and HClO. After binding with Zn2+ at a molar ratio of 1:1, the fluorescence intensity (λex = 482 nm, λem = 653 nm) of the probe was significantly enhanced, thus achieving quantitative detection and optical cell imaging of Zn2+. The complexation constant (K) of the probe with Zn2+ was 2.34 × 104 M−1. The response time of the probe for Zn2+ was less than 20 s and the detection limit was 15.3 nM. Moreover, this probe also showed a specific response to HClO. After interacting with HClO, the fluorescence intensity of the probe was increased significantly with a red shift of the emission wavelength from 670 nm to 705 nm (λex = 550 nm). The response time and the detection limit of probe for HClO were 4 min and 1.39 μM, respectively. The probe was successfully applied for visual bioimaging of Zn2+ and HClO inside living cells. The recoveries of Zn2+ and HClO using the probe in actual water samples were satisfactory.

Study of Bioinorganic Ternary Complexes of Mn (II) with Antibiotics &amp; Aspirin by Polarographic Technique

Polarography was used to determine the stability constants (log b) of mixed ligand bioinorganic complexes of Mn (II) with some antibiotics as primary ligands and aspirin as secondary ligand at pH=7.30 ± 0.01 and ionic strength m=1.0 M NaClO4 at 298 K. The waves of Mn and its complexes were quasireversible. Mn (II) formed 1:1:1, 1:2:1 and 1:1:2 complexes. Stability of these complexes is explain on the basis of sizes and basic nature of these Ligands.

Interaction of the Fungal Metabolite Harzianic Acid with Rare-Earth Cations (La3+, Nd3+, Sm3+, Gd3+).

Rare-earth elements are emerging contaminants of soil and water bodies which destiny in the environment and effects on organisms is modulated by their interactions with natural ligands produced by bacteria, fungi and plants. Within this framework, coordination by harzianic acid (H2L), a Trichoderma secondary metabolite, of a selection of tripositive rare-earth cations Ln3+ (Ln3+ = La3+, Nd3+, Sm3+, and Gd3+) was investigated at 25 °C, and in a CH3OH/0.1 M NaClO4 (50/50 w/w) solvent, using mass spectrometry, circular dichroism, UV–Vis spectrophotometry, and pH measurements. Experimental data can be satisfactorily explained by assuming, for all investigated cations, the formation of a mono-complex (LnL+) and a bis-complex (LnL2−). Differences were found between the formation constants of complexes of different Ln3+ cations, which can be correlated with ionic radius. Since gadolinium is the element that raises the most concern among lanthanide elements, its effects on organisms at different levels of biological organization were explored, in the presence and absence of harzianic acid. Results of ecotoxicological tests suggest that harzianic acid can decrease gadolinium biotoxicity, presumably because of complex formation with Gd3+.

Epoxidation of pillar[5]arene with three dimensional macrocyclic structure and host-guest capability for epoxy coatings

To expand the properties of epoxy coatings for emerging technologies, herein, a pillar[5]arene-based epoxy compound (PAEP) containing unique pillar-shaped three dimensional macrocyclic structure was prepared and cured with conventional 4,4′-diaminodiphenylmethane (DDM). Interestingly, the PAEP exhibited a strong host-guest complexation with 1,4-dibromobutane (DBrBu), a potential organic antibacterial agent, with a complex constant of 215.7 ± 11.02 M−1. Furthermore, the PAEP/DDM resin possessed enhanced mechanical and thermal properties, probably due to the increase of chain-entanglement brought about by the cyclic structure. Also, the PAEP/DDM resin exhibited excellent intrinsic flame retardant properties, including significantly reduced peak heat release rate (153.5 W·g−1) and high limit oxygen index (LOI) (34.7%), and a V-0 rating in the UL-94 test. Moreover, the PAEP/DDM resin exhibited a remarkably low dielectric constant of 2.25 at 106 Hz for telecommunication applications, which is much lower than the current epoxy resins with nanoporous inorganic modifiers. Therefore, the incorporation of pillar[5]arene is a fruitful pathway to expand the properties of epoxy resins and provides a new platform for decoration for various applications.

Rigidified Derivative of the Non-macrocyclic Ligand H4OCTAPA for Stable Lanthanide(III) Complexation.

The stability constants of lanthanide complexes with the potentially octadentate ligand CHXOCTAPA4–, which contains a rigid 1,2-diaminocyclohexane scaffold functionalized with two acetate and two picolinate pendant arms, reveal the formation of stable complexes [log KLaL = 17.82(1) and log KYbL = 19.65(1)]. Luminescence studies on the Eu3+ and Tb3+ analogues evidenced rather high emission quantum yields of 3.4 and 11%, respectively. The emission lifetimes recorded in H2O and D2O solutions indicate the presence of a water molecule coordinated to the metal ion. 1H nuclear magnetic relaxation dispersion profiles and 17O NMR chemical shift and relaxation measurements point to a rather low water exchange rate of the coordinated water molecule (kex298 = 1.58 × 106 s–1) and relatively high relaxivities of 5.6 and 4.5 mM–1 s–1 at 20 MHz and 25 and 37 °C, respectively. Density functional theory calculations and analysis of the paramagnetic shifts induced by Yb3+ indicate that the complexes adopt an unprecedented cis geometry with the two picolinate groups situated on the same side of the coordination sphere. Dissociation kinetics experiments were conducted by investigating the exchange reactions of LuL occurring with Cu2+. The results confirmed the beneficial effect of the rigid cyclohexyl group on the inertness of the Lu3+ complex. Complex dissociation occurs following proton- and metal-assisted pathways. The latter is relatively efficient at neutral pH, thanks to the formation of a heterodinuclear hydroxo complex.

Inhibition of Fenton Reaction of Glucose by Alcohols and Tetrahydrofuran in Catalytic Concentrations: Calculation of the Stability Constants of ROH/Fe2+ Complexes

Background: The Fenton reaction is of growing interest due to its primary function in bodily processes and industrial waste disposal. However, the effects of alcohol on this reaction have not been addressed. Therefore, we analyze for the first time the role that catalytic concentrations of alcohols play in the Fenton reaction. Methods: The Fenton reaction was carried out by measuring oxidation-reduction potential and pH monitoring under dark conditions to avoid photochemical reactions. The reaction end point was established using the first derivative of plotting potential versus time. This point was also checked by the dichromate test for hydrogen peroxide detection. Gas-liquid chromatography was used to measure alcohol content. The Fenton reaction of glucose was performed first, and then each alcohol, including ethanol, methanol, iso-propanol, and terbutanol, was added separately in catalytic amounts, as well as the cyclic ether tetrahydrofuran. The reaction rate constants and the stability constants of each complex formed were measured. Results: Alcohols were shown to inhibit the Fenton reaction by forming iron-alcohol complexes. An iron-tetrahydrofuran complex was also formed. The crucial oxygen role in the functional group of alcohols and ethers is supported by a reaction with tetrahydrofuran. These results also explain the difficulties in the disposal of sugar-enriched alcoholic industrial effluents. Conclusion: Our findings show that alcohols, such as ethanol, methanol, iso-propanol, and ter-butanol at catalytic concentrations, slow down the Fenton reaction due to decreased iron availability by forming iron (II)-alcohol complexes. The method is also useful for calculating stability constants for iron-alcohol and iron-tetrahydrofuran complexes, which are not otherwise easy to assess.

Fractionation of germanium and silicon during scavenging from seawater by marine Fe (oxy)hydroxides: Evidence from hydrogenetic ferromanganese crusts and nodules

Germanium (Ge) and silicon (Si) are an element pair which shows rather coherent behaviour in many geochemical systems. In aqueous systems and in the critical zone, however, Ge and Si may fractionate from each other, leading to slight differences between the Ge/Si ratios of continental crust, river water and seawater. We here show that even stronger fractionation of the GeSi couple occurs within seawater during the formation of hydrogenetic ferromanganese (FeMn) crusts and nodules. We determined Ge/Si ratios of hydrogenetic FeMn crusts from the Pacific Ocean following a new analytical approach using laser-ablation ICP-MS on nano-particulate tablets prepared from the FeMn crust material. Data quality was monitored and demonstrated by repetitive measurements of FeMn nodule reference material (RM) NOD-P1 from the Pacific Ocean (Ge/Siwt: 16.8 × 10−6 g/g; Ge/Simol: 6.47 × 10−6 mol/mol), which is the only RM for which high-quality GeSi reference data are available. We also report Ge/Si ratios for FeMn nodule RMs NOD-A1 from the Atlantic Ocean (Ge/Siwt: 24.9 × 10−6; Ge/Simol: 9.6 × 10−6) and for JMn-1 from the Pacific Ocean (Ge/Siwt: 17.9 × 10−6; Ge/Simol: 6.9 × 10−6). The Ge/Siwt ratios of the hydrogenetic FeMn crusts from the Pacific Ocean range from 13.2 × 10−6 to 33.5 × 10−6 (Ge/Simol: 5.1 × 10−6 to 13 × 10−6). The Ge/Si ratios of both FeMn crusts and nodules are significantly higher than those of ambient seawater (ca. Ge/Siwt: 1.7 × 10−6; Ge/Simol: 0.7 × 10−6). Their Ge/Si ratios are also well-above those of potential (alumino)silicate detritus. Hence, these high Ge/Si ratios reveal fractionation of Ge and Si during scavenging from seawater by the iron (oxy)hydroxide component in FeMn crusts, and do not result from the presence of detrital material in the chemical precipitate. Their high Ge/Si ratios relative to seawater also suggest that despite higher complexation constants with organic ligands for Ge than Si, dissolved organic ligands do not control marine GeSi fractionation via preferential retention of Ge in seawater.

Exploring Interaction Dynamics of Designed Organic Charge Transfer Complex of 6-Aminoindole and Chloranilic Acid: Spectrophotometric, Characterization, Computational, Antimicrobial, and DNA Binding Properties

The chemistry of a new charge and proton transfer hydrogen bonded complex (PT CT) between the donor 6-Aminoindole (6 AMI) and the π-acceptor Chloranilic acid (CLA) has been explored in acetonitrile (ACN), methanol (MeOH), and 50% acetonitrile + 50% methanol (ACN-MeOH) at 25 °C by using electronic absorption spectroscopy. By exploiting Job's and the photometric titration methods, the molar proportion of the PT CT complex was confirmed as 1:1. The modified Benesi-Hildebrand principle was used to evaluate the association constant (KCT) and molar absorptivity (ƐCT) of the PT CT complex, and these values indicate that the produced PT CT complex is more stable. In three different solvents, the effect of solvent polarity on charge transfer spectra was also observed. Different spectroscopic physical parameters were assessed in different polar solvents, including energy (ECT), ionization potential (ID), resonance energy (RN), oscillator strength (f), dissociation energy (W), standard gibbs free energy (ΔGo), transition dipole movement (μEN), and these were also within the accepted values, confirming the stability of the formed PT CT complex. The produced solid PT CT complex was analyzed by using FT-IR, NMR, TGA-DTA, and SEM-EDX spectra. Powder XRD analysis was used to determine the PT CT complex nature and crystalline size. The biological activity of the current PT CT complex has been screened in antimicrobial and DNA binding studies. The synthesized PT CT complex was shown to have excellent antimicrobial activity and DNA binding affinity. Therefore, in the future, it may be used as a pharmaceutical drug for bacterial and fungal infections. The computational studies were carried out by using DFT analysis, and the functions were used to B3LYP and CAM B3LYP in the gas phase, with the basis set being 6-31G + (d, p). The bond lengths, bond angles, Mulliken atomic charges, MEP maps, reactivity parameters, and FMO surfaces were also calculated. The computational analysis is additionally supported by the experimental studies of the PT CT complex.