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PubMed1981

Permethyl analogue of the pyrrolic antibiotic distamycin A.

The synthesis of an analogue of distamycin A, a pyrrolic oligopeptide possessing antiviral and antibiotic activity, is described in which each of the three pyrrole rings is fully methylated. This structural modification results in pyrrole rings which are extraordinarily electron rich and required the development of a new synthetic approach to these polypyrrolic amides. The key reactions involved development of a general method for the synthesis of 3-aminopyrroles and for formation of an amide bond between a pyrrole-2-carboxylic acid and these 3-aminopyrroles. Since the acid is hindered, a poor electrophile, and acid sensitive, while the amine is unstable and a hindered, weak nucleophile, amide bond formation under the usual conditions was poor. A very efficient method, however, was developed involving the isolation of 1-hydroxybenzotriazole active ester prepared in situ from another active ester. Neither the mono-, di-, nor tripyrrolic permethyl analogues were effective antimalarials, and none showed anticancer activity.

Animals↗

PubMed1984

Antihypertensives. N-1H-Pyrrol-1-yl-3-pyridazinamines.

The hypothesis that the side effects of hydralazine, such as mutagenicity and lupus erythematosus like syndrome, might be due to the NHNH2 group prompted us to incorporate part of this moiety into a pyrrole ring. Therefore, we prepared a series of N-1H-pyrrol-1-yl-3-pyridazinamines and a limited number of N-1H-pyrrol-1-yl-1-phthalazinamines by reaction of 3-hydrazinopyridazines and 1-hydrazinophthalazines with gamma-diketones. Most of these compounds, especially in the pyridazine series, showed moderate to strong antihypertensive activity in spontaneously hypertensive rats. The decrease in blood pressure generally had a slow onset after either oral or intravenous administration. N-(2,5-Dimethyl-1H-pyrrol-1-yl)-6-(4-morpholinyl)-3-pyridazinamine hydrochloride (30) (MDL 899) showed no mutagenic activity in several tests and is now in clinical trials in patients.

Animals↗

PubMed2002

Cross-linking of proteins by 3-(trifluoromethyl)-2,5-hexanedione. Model studies implicate an unexpected amine-dependent defluorinative substitution pathway competing with pyrrole formation.

Protein modification by the neurotoxic gamma-diketone 3-methyl-2,5-hexanedione (3-MHD) and its analogue 3-(trifluoromethyl)-2,5-hexanedione (3-TFMHD) was examined. Unlike 3-MHD, which forms lysine-based pyrroles that lead to autoxidation-dependent protein cross-linking, 3-TFMHD forms an autoxidatively inert pyrrole. The surprising finding that 3-TFMHD was nonetheless as effective as 3-MHD in cross-linking ribonuclease A suggested that protein lysine condensation with 3-TFMHD could take an alternate course competing with pyrrole formation. Model studies using neopentylamine led to the isolation of the expected 1-(2,2-dimethylpropyl)-2,5-dimethyl-3-(trifluoromethyl)pyrrole as well as the neopentylamine-3-TFMHD 2:1 adducts N,N'-bis(2,2-dimethylpropyl)-2-amino-3-acetyl-5-methylpyrrole (major) and N,N'-bis(2,2-dimethylpropyl)-3-(1-aminoethylidene)-5-methyl-4-pyrrolin-2-one (minor). The formation of these 2:1 adducts, the lysine analogues of which are believed to be mainly responsible for the observed protein cross-linking, is proposed to proceed via Schiff base formation, enamine fluoride elimination, second amine condensation, and hydrolysis.

Cross-Linking Reagents↗

PubMed2005

Heterocyclic alpha-alkylidene cyclopentenones obtained via a Pauson-Khand reaction of amino acid derived allenynes. A scope and limitation study directed toward the preparation of a tricyclic pyrrole library.

The synthesis of a novel class of tricyclic pyrroles has been accomplished by using a Pauson-Khand/Stetter/Paal-Knorr reaction sequence. Full details of the Pauson-Khand reaction of amino acid tethered allenynes 4a-e and 9a-d are disclosed. The study of this reaction led to the discovery of an unprecedented substituent effect on the diastereoselectivity of the Mo(CO)6 mediated allenic Pauson-Khand reaction. It was found that amino acid tethered allenynes with aromatic side chains afford alpha-alkylidene cyclopentenones with the opposite diastereoselectivity compared to those with aliphatic side chains. This effect has been attributed to complexation of the metal mediator to the aromatic ring in the substrate. Furthermore, an isomerization of one of the diastereomers of the alpha-alkylidene cyclopentenones was encountered, leading to eventual decomposition. The stable diastereomers were found to react well in the Stetter reaction leading to 1,4-diketones that were converted to pyrroles. The observation that the first generation of 2-alkyl-substituted pyrroles was unstable led to a second generation of 2-carboxamide pyrroles with sufficient stability for biological tests which are in progress.

Alkynes↗

PubMedDate not supplied

Pyrroles as effective agents for blocking amine nitrosation.

The ability of 10 pyrroles to block the acidic nitrosation of morpholine has been determined by using an assay that measures their effectiveness in the presence of a 10-fold excess of amine. The log (% N-nitrosomorpholine) formed is a linear function of blocking agent concentrations ranging from 0.0 to 1.5 times the equivalents of initial nitrite. The negative slopes of these plots allow a ranking of the effectiveness of the blocking agent. Several of the pyrroles have been found to be much more effective than established blocking agents such as ascorbic acid. The following order of blocking ability has been determined: 2,5-dimethylpyrrole = 1-benzyl-2,5-dimethylpyrrole much greater than 4-methylcatechol greater than ascorbic acid = 1,2-phenylenediamine = pyrrole greater than 1,2,5-tribenzylpyrrole = 1-benzylpyrrole = octamethylporphine much greater than ammonium sulfamate = hydrazine = 2,5-diphenylpyrrole much much greater than beta-nicotyrine greater than 2-pyrrolecarboxylic acid. Pyrroles give complex mixtures devoid of N-nitroso compounds upon nitrosation.

Amines↗

PubMed1997

(Carboxyalkyl)pyrroles in human plasma and oxidized low-density lipoproteins.

Free-radical oxidation of human plasma low-density lipoprotein (LDL) produces (carboxyalkyl)pyrrole (CAP) epitopes that were detected with enzyme-linked immunosorbent assays using antibodies raised against keyhole limpet hemocyanin (KLH)-bound 2-(omega-carboxyheptyl)-pyrrole (CHP) and 2-(omega-carboxypropyl)pyrrole (CPP). These antibodies exhibit high structural selectivity (< 0.5% cross-reactivity) in competitive binding inhibition assays with the corresponding human serum albumin (HSA)-bound pyrroles. No cross-reactivity was detected for HSA-bound 2-pentylpyrrole, an epitope that is generated by a reaction of 4-hydroxy-2-nonenal (HNE) with protein lysyl residues. Oxidation of either arachidonic or linoleic acid in the presence of HSA produced an HNE-derived 2-pentylpyrrole epitope. However, only oxidation of linoleic acid formed HSA-bound CHP, while only oxidation of arachidonic acid generated HSA-bound CPP. Since ester hydrolysis with KOH markedly elevated levels of immunoreactive epitopes detected in oxidized LDL, the CAPs are presumably generated by reactions of oxidized cholesteryl esters, triglycerides, and phospholipids with LDL protein, and only some of these oxidized esters are hydrolyzed, e.g., by phospholipase activity associated with LDL. Protein-bound CHP immunoreactivity was detected in human plasma, and levels are significantly elevated in renal failure and atherosclerosis patients compared with healthy volunteers. This provides the first evidence for the biological occurrence of protein-bound CAPs in vivo and further suggests that free-radical oxidation of polyunsaturated lipids produces hydroxyalkenal carboxylate esters whose gamma-hydroxy-alpha,beta-unsaturated aldehyde functionality and reactivity resemble that of HNE.

Adjuvants, Immunologic↗

PubMed1996

Molecular site specificity of pyridinoline and pyrrole cross-links in type I collagen of human bone.

Compared with soft tissue collagens, bone type I collagen displays a distinctive pattern of covalent cross-linking, with evidence of preferred sites of molecular interaction and a prominence of both immature, divalent cross-links and mature, trivalent cross-links in the adult tissue. In this study the site-specificity of the mature cross-links in human bone collagen was examined. Peptides containing fluorescent pyridinoline cross-links and Ehrlich's-reactive pyrrole cross-links were isolated from a bacterial collagenase digest of demineralized bone matrix. The digest was fractionated by molecular sieve chromatography, monitoring for peptide absorbance, pyridinoline fluorescence, pyrroles by Ehrlich's reagent, and immunoassay for cross-linked N-telopeptides. Individual cross-linked peptides were resolved by ion-exchange and reverse-phase HPLC. Structures were established by NH2-terminal microsequencing, cross-link analysis, electrospray mass spectrometry, and immunoassay. Two, about equally occupied, sites of pyridinoline cross-linking were identified, N-telopeptide to helix and C-telopeptide to helix. Pyrroles were alternative cross-linking products at the same sites, but concentrated (85%) at the N-telopeptide end. Only one combination of chains was cross-linked by pyridinolines at the C-telopeptide to helix site, [alpha1(I)C]2alpha1(I)helix. Several peptide combinations arose from the N-telopeptide to helix site, but the main source of pyridinolines was from the locus, alpha1(I)Nalpha2(I)Nalpha1(I)helix. Pyridinolines linking two alpha1(N) telopeptides were a minor component. Pyrroles were concentrated at the locus, alpha1(I)Nalpha2(I)Nalpha2(I)helix. The cross-link ratio of hydroxylysylpyridinoline to lysylpyridinoline differed between N-telopeptide and C-telopeptide sites, and between the individual interchain combinations. Cross-linked N-telopeptides accounted for two-thirds of the total lysylpyridinoline in bone. N-telopeptide pyridinoline fluorescence was quenched on chromatography, so that reliance on peptide fluorescence alone can underestimate the level of N-telopeptide pyridinoline cross-linking.

Adult↗

PubMed1997

4-hydroxy-2-nonenal pyrrole adducts in human neurodegenerative disease.

Increasing age and inheritance of the epsilon 4 allele of apolipoprotein E (APOE4) are significant risk factors for sporadic and late onset familial Alzheimer disease (AD); however, the mechanisms by which either leads to AD are unknown. Numerous studies have associated advancing age with increased indices of oxidative challenge to brain, and with still further increased oxidative damage to relevant brain regions in AD patients. A major consequence of oxidative damage to brain is lipid peroxidation with production of the neurotoxic metabolite 4-hydroxy-2-nonenal (HNE). HNE reacts with protein to yield several adducts, including a pyrrole adduct that forms irreversibly in biological systems. Previously, we have shown in a small number of AD and control patients that HNE pyrrole adduct antiserum is immunoreactive with neurofibrillary tangles (NFT), and that this reactivity was significantly associated with inheritance of APOE4. Others have confirmed this pattern of immunoreactivity in AD brain but did not observe an association with APOE4. Herein, we have expanded the study group to 19 AD patients homozygous for APOE4 or APOE3, as well as 30 patients with other neurodegenerative diseases, including diffuse Lewy body disease, Pick's disease, progressive supranuclear palsy, Parkinson's disease, and human immunodeficiency virus-1 encephalitis. HNE pyrrole adduct immunoreactivity on NFT in AD patients was strongly associated with APOE4 homozygosity. With the exception of rare immunoreactive Pick bodies in one case of Pick's disease, no other structure was recognized by HNE pyrrole adduct antiserum in this series of patients. We propose that there is a significant difference between the interaction of apoE3 and apoE4 with lipid peroxidation in the brains of AD patients.

Adult↗

PubMed1988

Researches on antibacterial and antifungal agents. IX--Pyrrole analogues of bifonazole with potent antifungal activities.

The synthesis and antifungal activities of pyrrole analogues of bifonazole are reported. Reduction of 4-nitrobenzophenone to the corresponding alcohol, reaction with phosphorus tribromide of the latter compound and condensation of the bromonitroderivative with imidazole led to 1-[alpha-(4-nitrophenyl)-4'-benzyl]-1H-imidazole. Hydrogenation of the nitro group to amino and reaction with 2,5-dimethoxytetrahydrofuran according to the Clauson-Kaas procedure afforded the pyrrole analogue of bifonazole. This compound and the related chloroderivative were also prepared by a similar pathway starting from 4-(1H-pyrrol-1-yl)benzophenone and its 4'-chloroderivative. Microbiological screening against Candida albicans and Candida spp showed 1-(alpha-[4-(1H-pyrrol-1-yl)phenyl]benzyl)-1H-imidazole to be the most active compound among the tested derivatives.

Antifungal Agents↗

PubMedDate not supplied

Metabolic activation of model pyrroles by cytochrome P-450.

1,3,4-Trimethylpyrrole and 1-methyl-3,4-bis(hydroxymethyl)pyrrole were synthesized and labeled with tritium in the C3 and C4 substituents. Both pyrroles were covalently bound to protein, DNA, and RNA when administered to rats in vivo; the level of binding of the trimethyl compound was an order of magnitude higher than that of the diol in liver. Binding of both pyrroles to protein in vitro was catalyzed by microsomal fractions in the presence of NADPH but not NADH, and the enzymatic activation of the trimethyl compound was inhibited by SKF 525-A, CO, anaerobiosis, or reduced glutathione. The microsomal fractions could be replaced by reconstituted systems containing highly purified NADPH-cytochrome P-450 reductase and cytochrome P-450 in catalyzing the activation of the trimethyl compound. These results indicate that cytochromes P-450 can activate pyrroles to more electrophilic species capable of binding irreversibly to biological macromolecules.

Animals↗

PubMed2003

CloN6, a novel methyltransferase catalysing the methylation of the pyrrole-2-carboxyl moiety of clorobiocin.

The aminocoumarin antibiotic clorobiocin contains a 5-methylpyrrole-2-carboxylic acid unit. This pyrrole unit is derived from L-proline, and it would be expected that its 5-methyl group should be introduced by a methylation reaction. However, sequence analysis of the clorobiocin biosynthetic gene cluster did not reveal a gene with sequence similarity to the SAM-dependent methyltransferases that could be assigned to this reaction. This study, however, has provided evidence that the gene cloN6 is involved in this methylation reaction. Its gene product CloN6 shares conserved sequence motifs with the recently identified radical SAM protein superfamily, and it has been suggested that members of this family can catalyse methylcobalamin-dependent methylation reactions. cloN6 was inactivated in the clorobiocin producer Streptomyces roseochromogenes var. oscitans DS 12.976 by use of the PCR-targeting method. The cloN6(-) mutants accumulated, instead of clorobiocin, a derivative lacking the 5"'-methyl group of the pyrrole moiety (termed novclobiocin 109). A structural isomer carrying the pyrrole-2-carboxyl moiety at 2"-OH rather than at the 3"-OH of the deoxysugar (novclobiocin 110), and a derivative completely lacking the pyrrole unit (novclobiocin 104) were also identified. The structures of the metabolites were confirmed by NMR and MS analysis. Antibacterial activity tests against Bacillus subtilis showed that novclobiocin 109 and novclobiocin 110 have antibacterial activities about eight times less than that of clorobiocin, whereas novclobiocin 104 showed no activity under the test conditions.

Anti-Bacterial Agents↗

PubMed2007

Exploring the dynamics of calix[4]pyrrole: effect of solvent and fluorine substitution.

Molecular dynamics simulations show that calix[4]pyrrole (CP) and octafluorocalix[4]pyrrole (8F-CP) are extremely flexible molecules. CP mainly adopts the 1,3-alternate conformation in all the solvents, although the percentage of alternative conformations increases in polar solvents, especially those with good hydrogen-bonding acceptor properties. However, in the case of 8F-CP, the cone conformation is the most populated in some solvents. Transitions between conformers are common and fast, and both CP and 8F-CP can adopt the cone conformation needed for optimum interaction with anions more easily than would be predicted on the basis of previous gas-phase calculations. Furthermore, the present studies show that when a fluoride anion is specifically placed initially in close proximity to CP and 8F-CP in their respective 1,3-alternate conformations, an extremely fast change to the cone conformation is observed in both cases. The results suggest that preorganization does not represent a major impediment to anion-binding for either CP or 8F-CP, and that ion-induced conformational changes can follow different mechanisms depending on the solvent and the chemical substituents present on the calix[4]pyrrole beta-pyrrolic positions.

Calixarenes↗

PubMed2005

Reduction of a 4-pyrrole phenylacyl-containing peptide with trifluoroacetic acid-triisopropylsilane-phenol-H2O during solid-phase peptide synthesis and its protein kinase C alpha inhibitory activity.

Cleavage of 4-pyrrole phenylacyl TentaGel-appended peptide (5) containing Arg(Pbf) with trifluoroacetic acid/triisopropylsilane/phenol/H2O (90/2/4/4) gives the 4-pyrrole phenylacyl peptide (3). However, cleavage of 4-pyrrole phenylacyl Rink-appended peptide (7) containing Arg(Pbf) using the same reagents furnishes the 4-pyrrolidine phenylacyl peptide (8), which contains the reduced pyrrole ring. Compound 8 displays a Ki of 2.32 microM, approximately fivefold less potent than compound 3.

Amino Acid Sequence↗

PubMed1996

Synthesis and Characterization of a New Series of Nickel(II) meso-Tetrakis (polyfluorophenyl)porphyrins Functionalized by Pyrrole Groups and Their Electropolymerized Films.

A new series of nickel(II) meso-tetrakis(polyfluorophenyl)porphyrins functionalized by pyrrole groups have been synthesized. Each new complex was isolated and characterized by (1)H NMR, (19)F NMR, IR, UV-visible spectroscopy, and mass spectrometry as well as electrochemistry. This is the first example of polyfluorinated substituted porphyrins where the four possible compounds have been obtained by functionalization of the para-fluorine substituents of the nickel(II) meso-tetrakis(pentafluorophenyl)porphyrin. This functionalization has allowed the preparation for the first time of polyfluorinated metalloporphyrin films by oxidative electropolymerization. Electrochemical stability studies of these polymeric films have shown better stability for films derived from the monomer having four pyrrole groups because of their high degree of cross-linking degree. A large difference of electroactive solute permeation has been found in the polymeric films which have been obtained by electropolymerization of monomers for which one pyrrole group has been substituted compared to those for which four pyrrole groups have been substituted. This could be related to quite rigid polymer structures for tetrasubstituted polymer films and molecular sieving properties of monosubstituted polymer films. The spectroelectrochemistry of a polymeric film on an OTE has established that the two-electron-oxidized species are stable in the film; likewise the singly and doubly electroreduced species are stable and are more likely ligand-centered.

Journal Article↗

PubMed2006

Nonlinear optical properties of alkalides Li+(calix[4]pyrrole)M- (M = Li, Na, and K): alkali anion atomic number dependence.

A new type of alkalide compound, Li+(calix[4]pyrrole)M- (M = Li, Na, and K), is presented in theory, which may be stable at room temperature. It has been shown by our calculations that the first hyperpolarizability (beta) is considerably large by means of the density functional theory method. The beta values are determined at the B3LYP/6-311++G level (for the alkali atoms the 6-311++G(3df) basis set is employed) as 8.9 x 103, 1.0 x 104, and 2.4 x 104 au for M = Li, Na, and K, respectively. These beta values are much larger than that of electride Li+(calix[4]pyrrole)e- (beta = 7.3 x 103 au) by a factor of 1.2 to 3.4. Comparing to the cryptand calix[4]pyrrole, the beta values of Li+(calix[4]pyrrole)M- are enhanced by 20-60 times. It is revealed, for the first time, that the beta value of alkalide compounds depends on the atomic number of the alkali anion, and it can be enhanced by choosing the akali anions with larger atomic numbers. The alkali anion in the alkalide compound decreases the transition energy and also increases the oscillator strength of the main transition, consequently the beta value is enhanced. This study proposes such a novel way to synthesize and design new NLO materials by using the alkali atom with a larger atomic number to create an anion in alkalide compounds.

Journal Article↗

PubMed1999

Synthesis and antitumor activity of duocarmycin derivatives: modification of segment-A of A-ring pyrrole compounds.

A series of 3-substituted A-ring pyrrole compounds of duocarmycin were synthesized and evaluated for in vitro anticellular activity against HeLa S(3) cells and in vivo antitumor activity against murine sarcoma 180 in mice. These compounds were evaluated on the peripheral blood toxicity and delayed lethal toxicity. Further, to expand our investigation of their peripheral blood toxicity, the toxicity to bone marrow cells (CFU-GM, CFU-Meg) was investigated. Among 3-substituted A-ring pyrrole compounds of duocarmycin bearing a 5',6',7'-trimethoxy-2'-indolecarboxyl group as segment-B (Seg-B), several analogues showed remarkably potent antitumor activity with low peripheral blood toxicity. The 3-formyl compound 12h, one of such analogues, showed stronger antitumor activity with lower toxicity to bone marrow cells compared to DU-86 (2a), an active metabolite of KW-2189 (2b). However, compound 12h caused delayed death. On the other hand, the 3-bromo compound 15f, one of the 3-substituted A-ring pyrrole derivatives bearing a 4'-methoxycinnamoyl group as Seg-B, showed the most potent antitumor activity among the 4'-methoxycinnamate analogues with low toxicity to bone marrow cells. Furthermore, compound 15f did not cause delayed death similarly to 2d. These results would indicate the importance of the C-3 substituents of A-ring pyrrole duocarmycin derivatives for exhibiting antitumor activity and decreasing toxicity.

Animals↗

PubMed1996

1,4-Disubstituted and 1,4,5-Trisubstituted 2-[(Benzotriazol-1-yl)methyl]pyrroles as Versatile Synthetic Intermediates.

The CH(2)Bt substituent, unlike previously used CH(2)X substituents, enables (i) the synthetic elaboration of pyrroles with unsubstituted ring positions and (ii) electrophilic as well as nucleophilic substitutions to give pyrroles of type pyrrolyl-2-CHENu. Thus, 1,4-disubstituted (7) and 1,4,5-trisubstituted 2-[(benzotriazol-1-yl)methyl]pyrroles (15) were easily prepared from the reaction of 5-(benzotriazol-1-yl)-1,2-epoxy-3-pentynes 4 or 14 with primary amines in i-PrOH. The 2-(benzotriazol-1-yl)methyl side chains of compounds 7 and 15 were elaborated by nucleophilic substitution and also by initial alkylation followed by replacement or elimination of the benzotriazolyl moiety to afford a variety of 1,2,4-trisubstituted (6, 8-9, 11-13) and 1,2,4,5-tetrasubstituted pyrroles (18, 20-22).

Journal Article↗

PubMed2006

New insights on anion recognition by isomers of a calix pyrrole derivative.

Two isomeric structures of meso-tetramethyltetrakis(3-hydroxyphenyl)calix[4]pyrrole, 4-alphaalpha betabeta and 4-alphabeta alphabeta, have been isolated and characterized by 1H NMR in different solvents (CD3CN, CD3OD, and DMSO-d6) at 298 K. Standard Gibbs energies of solution derived from solubility data in various solvents were used to calculate the transfer Gibbs energy, delta(t)G(o), of these ligands using acetonitrile as the reference solvent. These results are consistent with the 1H NMR studies in different media that show chemical shift changes observed in the resonances of the NH and the OH protons of these ligands. Solvate formation was observed when these isomers were exposed to saturated atmosphere of N,N-dimethylformamide, dimethyl sulfoxide and propylene carbonate. Anion interaction involving 4-alphaalpha betabeta and 4-alphabeta alphabeta was investigated by 1H NMR in CD3CN while the complex composition was assessed through conductance measurements. Significant differences are observed in the affinity of these ligands for anions as well as in the composition of the fluoride complexes. Thus 4-alphaalpha betabeta shows selectivity for H2PO4(-) in acetonitrile while its isomer 4-alphabeta alphabeta is selective for the fluoride anion. Again the complex composition is altered for the fluoride anion when complexed with 4-alphaalpha betabeta in acetonitrile (1:1 complex) relative to 4-alphabeta alphabeta in the same solvent. The latter isomer shows an enhanced hosting ability for this anion. Thus two anions are taken up per unit of ligand. The thermodynamics of complexation of H2PO4(-) and these ligands in acetonitrile is discussed, and the results are compared with those involving calix[4]pyrrole and this anion in this solvent. It is shown that the isomers interact with two H2PO4(-) anions while one calix[4]pyrrole unit interacts with this anion. This paper demonstrates for the first time that the enthalpy parameter may be a suitable reporter of the number of hydrogen bonds formed when calix[4]pyrrole and its derivatives interact with the dihydrogen phosphate anion in acetonitrile. In moving from acetonitrile to N,N-dimethylformamide, 4-alphaalpha betabeta is unable to enter complexation with most anions, except fluoride, with which the formation of a 1:2 (ligand:anion) complex is demonstrated. The rather versatile behavior of these receptors for anions is explained on the basis of 1H NMR evidence and solvation effects. These investigations highlight the importance of the medium effect on the stability of the complex and reflect the inherent nature of the solvent and its highly significant involvement in the complexation process.

Journal Article↗