Ligands In Aqueous Media Research Articles

Supramolecular architectures, Hirshfeld surfaces analysis, spectroscopic, computational and photovoltaic properties of nickel(II) binary and ternary complexes of N-phenethyl-iminodiacetate (2-) chelate

The bluish-green color nickel(II) binary and/or ternary compounds have been isolated from the solution of stoichiometric reaction between Ni(II) hydroxy-carbonate and N-phenethyl-iminodiacetic acid (H2pheida) chelating ligand in aqueous media with compound (2); [Ni(pheida)(Him)3]·4H2O and without imidazole compound (1); [Ni(pheida)(H2O)3]. The crystal pattern of binary compound [Ni(pheida)(H2O)3] (1) differs from the related tetra-hydrated ternary complex of [Ni(pheida)(Him)3]·4H2O (2) can be attributed to the presence of stronger N-(Him) spacer of imidazole ligand. The compounds reported herein, have been characterized by means of elemental analysis, FTIR, UV–vis, TGA and X-ray crystallography. Moreover, the distinctive inter-molecular forces particularly H-bonding interactions, 2D fingerprint plots and supramolecular architecture have been studied using Hirshfeld surface analysis. The nickel(II) binary and ternary complexes (1) and (2) show distorted octahedral geometry around the Ni(II) ion of the type 1 + 2 + 2 + 1 imposed by 3d8 electronic configuration with degenerate fully and half occupied t2g6 and eg2 orbitals respectively. The higher John-Teller distortion has been observed for complex (2) than that of complex (1). The IDA arm of chelate adopted fac-NO2 conformation in both complexes (1) and (2). Moreover, the photovoltaic properties as semiconducting nature for ligand and their corresponding Ni(II) complexes were estimated using Tauc’s equation, αhν = A(hν-Eg)r, where r = ½ for indirect and 2 for direct electronic transitions through UV–vis absorption data. The indirect and direct electronic transition bandgap (Eg) calculated for complex (1) is 2.0 and 3.07 eV respectively. Similarly, 2.55 and 4.39 eV respectively measured for complex (2).

Evaluation of NO Release Capability from Dinitrosyl Iron Complexes (DNIC) Containing Biomolecules as Ligands in Aqueous Media

Evaluation of NO Release Capability from Dinitrosyl Iron Complexes (DNIC) Containing Biomolecules as Ligands in Aqueous Media

Palladium-Catalyzed Suzuki−Miyaura cross-coupling reactions employing hydrazone-thioether ligands in aqueous media under IR-irradiation

An in situ catalytic system was generated based on hydrazone-thioether ligands and Pd(OAc)2. It provided excellent catalytic activity in the Suzuki-Miyaura cross-coupling reactions between aryl halides and arylboronic acids in aqueous medium and under IR irradiation. The resulting coupled products were obtained in short reaction times, with low catalyst loads and in good to excellent yields. Density functional theory based computations were applied to characterize the probable structure of the dimeric complex formed between the hydrazone and Pd(OAc)2, afterwards structure was confirmed by experimental analysis of IR and ESI mass spectrometry.

Nickel (II) coordination polymer using pyrazine linkers and phthalate counter-anion: Synthesis, crystal structure, Hirshfeld surface and voids analysis

Herein, a new Ni(II) carboxylate polymer, [Ni(Pyr).4H 2 O]Phth , is synthesized by the reaction of NiSO 4 .7H 2 O with equimolar amounts of phthalic acid (PhthH 2 ) as the counter-anion and pyrazine (Pyr) as an ancillary ligand in aqueous media. The crystal structure of [Ni(Pyr).4H 2 O]Phth is investigated by single crystal X-rays diffraction analysis, which inferred the ionic nature of the complex. In cation, the Ni-center is coordinated by two pyrazine rings and four water molecules to form an octahedral coordination geometry. The crystal structure exists as a one-dimensional polymeric structure. The crystal packing is stabilized by OH O and CH O bonding. The non-covalent interactions are investigated by Hirshfeld surface analysis. The enrichment ratio delivers the tendency of the interaction of the pair of chemical moieties, which are involved in the packing of crystals. Moreover, void analysis is executed to look at the packing efficiency, which helps in predicting the mechanical response of the compound.

Prolinamide plays a key role in promoting copper-catalyzed cycloaddition of azides and alkynes in aqueous media via unprecedented metallacycle intermediates

Room temperature copper-catalyzed cycloaddition of azides and alkynes (CuAAC) proceeds in the presence of a prolinamide ligand in aqueous media via unique metallacycles.

Electrochemical and spectral studies of binary and mixed-ligand copper(II) and cobalt(II) complexes with 2,6-dipicolinic acid and bathophenanthroline chelating ligand in aqueous medium

• Preparation of binary copper(II) and cobalt(II) complexes with 2,6-dipicolinic acid in aqueous medium(1: 2 and 1: 10 molar ratios). • Preparation of mixed ligand copper(II) and cobalt(II) complexes with 2,6-dipicolinic acid and bathophenanthroline in aqueous medium(in 1: 1: 1 and 1: 2: 1 molar ratios). • Cyclic voltammetric studies of binary and mixed ligand copper(II) /cobalt complexes in aqueous medium(in 1: 2, 1: 10, 1: 1:1, 1: 2: 1 molar ratios), containing 0.2 M NaClO4. • UV-Visible spectroscopy of binary and mixed ligand copper(II)/cobalt(II) complexes(1: 2, 1: 10, 1: 1: 1 and 1: 2: 1 molar ratios) in aqueous medium. In this paper, we reported the preparation of four copper(II) and cobalt(II) complexes viz; [Cu(dipic) n (H 2 O) n ] 1, [Cu(dipic) n (bathophen) n ].nH 2 O 2, [Co(dipic) n (H 2 O) n ] 3, and [Co(dipic) n (bathophen) n ].nH 2 O 4 (where, n is the number of ligands attached and it could be 1 or 2), in different molar ratios; 1:2, 1:10, 1:1:1 and 1:2:1 in aqueous medium. All these complexes ( 1–4 ) were characterized by cyclic voltammetry and electronic absorption spectroscopy in different molar ratios as mentioned above. The 2,6-dipicolinic acid (dipic) and 4,7-diphenyl-2,9-dimethyl-1,10-phenanthroline (bathophen) used as primary and secondary ligands, respectively. The electrochemical behavior of binary copper(II) complex 1 with 2,6-dipicolinic acid in 1:2 and 1:10 molar ratios were showed a quasi-reversible single electron transfer redox couple Cu 2+/+ from +1000 mV to -200 mV potential limit (at 25 mVs −1 to 300 mVs −1 ) with easier reduction potential with increasing scan rate/concentration of ligand in binary complex 1 , containing 0.2 M NaClO 4 as a supporting electrolyte at glassy carbon working electrode. The redox behavior of mixed-ligand complex 2 with 2,6-dipicolinic acid and bathophen (in 1:1:1 and 1:2:1 molar ratios) shows similar pattern to that of complex 1 . The complex 2 showed an additional anodic peak potential (Epa’) due to oxidation of complex chemical species present in solution which is assigned to Cu 0/+2 , while during cathodic scaning it does not show any cathodic peak potential (Epc’), corresponding to (Epa’). The cyclic voltammetric studies of complexes 3 and 4 have also been done in aqueous medium. The observations of complexes 3 and 4 were totally different to that of the complexes 1 and 2 . The anodic scanning was started from +0.0 mV to -1500 mV potential limit (25 mVs −1 to 300 mVs −1 ), showed two pairs of redox couples and which are assigned to Co 2+/3+ and Co 2+/+ , respectively (in 1:1:1 and 1:2:1 molar ratios), quasi-reversible single electron transfer redox couples. The electrochemical behavior of complex 4 (in 1:1:1 and 1:2:1 molar ratios) showed similar behavior to that of binary complex 3 but different electrode potentials, confirmed to complexation. The UV-Vsibile spectroscopy of the binary and mixed ligand complexes ( 1–4 ) has also been done in aqueous medium (different molar ratios). The results of CV and UV-Visible spectral studies indicate that the geometry around the central metal ions is octahedral, in aqueous medium.

A Study of Uranyl (VI) Chloride Complexes in Aqueous Solutions under Hydrothermal Conditions using Raman Spectroscopy

The transport and deposition of uranium under hydrothermal conditions in the Earth’s crust has been a subject of ongoing study but is yet to be completely understood. In addition, there is little known about the fate of nuclear waste, consisting of uranium from spent fuel and other radioactive materials, upon storage in repositories or in nuclear reactor facilities. Because the nuclear waste often comes in contact with aqueous fluids in storage environments, studies of uranyl complexation with chloride and other ligands in aqueous media, to high temperature and pressure conditions, are needed. The primary purpose of this study was to investigate the speciation of aqueous uranyl (VI) chloride complexes, in solutions having a 0.05 M uranyl concentration and [Cl] concentrations ranging from 0.2 M to 6 M, under hydrothermal conditions. The aqueous uranyl chloride complexes in the samples were studied using Raman spectroscopy and the hydrothermal diamond anvil cell (HDAC), at temperatures up to 500 °C and pressures up to ~ 0.5 GPa. The uranyl bond stretching band feature occurring in the ~810 to 870 cm-1 region was fitted using the Voigt peak shape to determine the speciation of the equilibrium uranyl chloride complexes present in the samples. As expected, the n integer value of the UO2Cln+2-n complex species increases with the increase in temperature and chloride concentration, generally trending toward charge neutrality at high temperatures.

Chemical and photochemical behavior of ruthenium nitrosyl complexes with terpyridine ligands in aqueous media.

The synthesis and behavior in water of a set of various cis(Cl,Cl)-[R-tpyRuCl2(NO)](PF6) and trans(Cl,Cl)-[R-tpyRuCl2(NO)](PF6) (R = fluorenyl, phenyl, thiophenyl; tpy = 2,2':6',2''-terpyridine) complexes are presented. In any case, one chlorido ligand is substituted by a hydroxo ligand and the final species arises as a single trans(NO,OH) isomer, whatever the nature of the starting cis/trans(Cl,Cl) complexes. Six X-ray crystal structures are presented for cis(Cl,Cl)-[thiophenyl-tpyRuCl2(NO)](PF6) (cis-3a), trans(Cl,Cl)-[thiophenyl-tpyRuCl2(NO)](PF6) (trans-3a), trans(NO,OH)-[phenyl-tpyRu(Cl)(OH)(NO)](PF6) (4a), trans(NO,OH)-[thiophenyl-tpyRu(Cl)(OH)(NO)](PF6) (4b), trans(NO,OEt)-[phenyl-tpyRu(Cl)(OEt)(NO)](PF6) (5a), and trans(NO,OH)-[phenyl-tpyRu(Cl)(OEt)(NO)](PF6) (5b) compounds. The different cis/trans(Cl,Cl) complexes exhibit an intense low-lying transition in the λ = 330-390 nm range, which appears to be slightly blue-shifted after Cl → OH substitution. In water, both cis/trans(Cl,Cl) isomers are converted to a single trans(NO,OH) isomer in which one chlorido- is replaced by one hydroxo-ligand, which avoids tedious separation workout. The water stable trans(NO,OH)-species all release NO with quantum yields of 0.010 to 0.075 under irradiation at 365 nm. The properties are discussed with computational analysis performed within the framework of Density Functional Theory.

Bi-functional quantum dot-polysaccharide-antibody immunoconjugates for bioimaging and killing brain cancer cells in vitro

The most common primary brain tumors in adults are gliomas, where glioblastoma multiforme is one of the deadliest in humans. In this study, we engineered novel nanoconjugates composed of Ag-In-S/ZnS quantum dots directly stabilized by chitosan polysaccharide ligand in aqueous medium and biofunctionalized with monoclonal antibody against vascular endothelial growth factor (VEGF) receptors. These nano-immunoconjugates demonstrated bi-functional capabilities combining fluorescent emission for bioimaging and killing activity towards brain cancer cells with very promising perspectives in nanotheranostic applications.

Sonochemical synthesis of fluorescent 1,4-disubstituted triazoles using l-phenylalanine as an accelerator ligand in aqueous media

A green sonochemical protocol using l-phenylalanine as a water soluble promotor ligand has been developed for the regioselective synthesis of fluorogenic 1,4-disubstituted triazoles (3a-o) via well-known click reaction at 40 °C. l-Phenylalanine is a biocompatible, economical, commercially available and non-toxic ligand which not only serves to stabilize Cu(I) oxidation state but also prevents its disproportion to enhances and modulate the rate of reaction. The designed catalytic system exhibits broad substrate compatibility and can be recycled up to 5 cycles without appreciable loss in the yield of desired product. Gram scale synthesis was successfully accomplished with 92% yield.

A Remarkable Effect of Aluminum on the Novel and Efficient Aqueous-Phase Hydrogenation of Levulinic Acid into γ-Valerolactone Using Water-Soluble Platinum Catalysts Modified with Nitrogen-Containing Ligands

The catalytic performance of novel water-soluble platinum catalysts modified with various nitrogen-containing and phosphine ligands in the hydrogenation reaction of levulinic acid (LA) into γ-valerolactone (GVL) has been studied in environmentally attractive, green, aqueous monophasic systems. The presence of the Lewis acid aluminum enormously increases the catalytic activity of water-soluble platinum catalysts modified with nitrogen-containing ligands in the LA hydrogenation reaction and high catalytic activities up to 3540 TOF’s per hour with a quantitative selectivity towards GVL have been achieved using Na2PtCl6·6H2O precursors modified with the bidentate bathophenanthrolinedisulfonic acid disodium salt (BPhDS) ligand and low amounts of AlCl3·6H2O promotors (molar ratio of AlCl3·6H2O/Pt = 0.17) in aqueous media. This unprecedented increase in catalytic activity with aluminum promotors for water-soluble transition metal catalytic systems in aqueous-phase hydrogenation reactions has not been described until now in the literature. The apparent activation energy of platinum catalyst modified with the monodentate nitrilotriacetic acid trisodium salt ligand in aqueous medium was calculated and amounts to a relative low value of 73.04 kJ mol−1 when one considers that in the LA hydrogenation reaction this catalyst reduces a less reactive keto group into alcohol functionality. A recycling experiment of the Pt/BPhDS/Al catalyst from the aqueous monophasic LA hydrogenation reaction mixture followed by biphasic recovery of the catalyst in active form from organic reaction products by extraction and simple phase separation of an aqueous/organic two-phase system formed after addition of diethyl ether has shown that the Pt/BPhDS/Al catalyst is stable without loss of activity and selectivity in a consecutive run.

MgTi(cat)3, a promising precursor for the preparation of Ti–MOFs?

A new Ti(IV) triscatecholate complex was prepared in aqueous conditions. Its crystal structure was solved, and the complex was fully characterized by multiple techniques, including thermogravimetric analysis, temperature dependent powder X-ray diffraction (XRD), as well as NMR and UV–Vis spectroscopies. Thanks to liquid-state NMR, it is shown that such a complex is simultaneously stable enough in water to avoid the hydrolysis of the Ti(IV) ion, while still being able to undergo ligand exchange. Eventually, preliminary experiments suggest that this precursor is suitable for the preparation of new MOFs built up from polycatecholate ligands in aqueous media.

Water-Stable, Fluorescent Organic−Inorganic Hybrid and Fully Inorganic Perovskites

Stabilization of perovskites without addition of foreign surface-passivating ligands in aqueous media is essential for their applications in optoelectronics, biomedical science, and catalysis. However, these materials instantly degrade in water due to its intrinsic ionic nature. By controlling the peripheral layer of octahedral perovskite geometry, we reproducibly synthesized a series of rod-shaped fluorescent hybrid perovskites in both acidic and basic media at ambient conditions in large scale without capping ligands. The band gap is tunable from the red to sky-blue region with sharp emission. The lead bromide perovskites are stable more than 6 months in water without structural change. Our simple synthetic route has resolved the longstanding problems for its practical application in aqueous environment.

"On Water'' Promoted Ullmann-Type C-N Bond-Forming Reactions: Application to Carbazole Alkaloids by Selective N-Arylation of Aminophenols.

The Ullmann-type cross coupling of a variety of aromatic, aliphatic amines with aryl halides is reported using a CuI-based catalytic system in combination with an easily accessible prolinamide ligand in aqueous media. The method is mild and tolerant to air, moisture, and a wide range of functional groups, providing a novel way to access a variety of aminated products. Secondary amines like heteroaromatic amines and nucleobases have also been used, affording the corresponding coupling products in good to excellent yields. Moreover, this method has been employed for chemoselective C-N arylation of aminophenols and further utilized for the synthesis of carbazole natural products, avoiding the protection and deprotection steps.

Front Cover: Catalytic Cooperativity, Nuclearity, and O2/H2O2 Specificity of Multi‐Copper(II) Complexes of Cyclen‐Tethered Cyclotriphosphazene Ligands in Aqueous Media (Eur. J. Inorg. Chem. 42/2017)

Front Cover: Catalytic Cooperativity, Nuclearity, and O₂/H₂O₂ Specificity of Multi‐Copper(II) Complexes of Cyclen‐Tethered Cyclotriphosphazene Ligands in Aqueous Media (Eur. J. Inorg. Chem. 42/2017)

Catalytic Cooperativity, Nuclearity, and O2/H2O2 Specificity of Multi‐Copper(II) Complexes of Cyclen‐Tethered Cyclotriphosphazene Ligands in Aqueous Media

AbstractInvited for the cover of this issue are the groups of Y. Ye from Zhengzhou University, China, A. Angerhofer from the University of Florida, USA, Y. Zhao from Xiamen University, China, and L.‐J. Ming from the University of South Florida, USA. The cover image shows the pathways for dinuclear catechol oxidation by CuII complexes of cyclotriphosphazene derivatives with up to six metal‐binding sites.

Catalytic Cooperativity, Nuclearity, and O2/H2O2 Specificity of Multi‐Copper(II) Complexes of Cyclen‐Tethered Cyclotriphosphazene Ligands in Aqueous Media

Three ligands L1, L2, and L3 with 2, 4, and 6 1,4,7,10‐tetraazacyclododecane (cyclen) moieties attached to a cyclotriphosphazene core, respectively, were synthesized, and oxidation activities of their CuII complexes were investigated. Aerobic oxidation of catechol by these complexes follows an intramolecular dinuclear pathway with significant cooperativity (i.e., θ ≈ 1.5 out of a maximum of 2 for two potential substrate binding sites) and kinetic constants (i.e., kcat = 17.5 × 10–3 s–1, Km = 2.8 mm, and quite remarkable catalytic specificity kcat/Km 12.5 m–1 s–1 per di‐Cu center), while that by untethered CuII–cyclen follows a bimolecular dinuclear pathway without noticeable cooperativity (θ = 0.96) and fourfold lower kcat, despite their similar dinuclear mechanisms. The proximity of CuII centers is suggested by EPR spectra and relaxations, showing a broad spectral component particularly in Cu6L3. Thermodynamic parameters also indicate the significance of multi‐CuII sites in the oxidative catalysis. Air is a more specific oxidation agent for the representative complex Cu2L1, showing 3.2‐fold higher catalytic specificity kcat/Km than H2O2 toward a catechol substrate. The research provides further molecular basis for future design of O2/H2O2‐specific oxidation of multi‐domain Cu complexes.

Development of a complementary PET/MR dual-modal imaging probe for targeting prostate-specific membrane antigen (PSMA)

We tried to develop a dual-modal PET/MR imaging probe using a straightforward one-pot method by encapsulation with specific amphiphiles. In this study, iron oxide (IO) nanoparticles were encapsulated with three amphiphiles containing PEG, DOTA and the prostate-specific membrane antigen (PSMA)-targeting ligand in aqueous medium. The diameter of the prepared nanoparticle DOTA-IO-GUL was 11.01±1.54nm. DOTA-IO-GUL was labeled with 68Ga in high efficiency. The DOTA-IO-GUL showed a dose-dependent binding to LNCaP (PSMA positive) cells via a competitive binding study against 125I-labeled MIP-1072 (PSMA-targeting agent). Additionally, PET and MR imaging results showed PSMA selective uptake by only 22Rv1 (PSMA positive) but not PC-3 (PSMA negative) in dual-tumor xenograft mouse model study. MR imaging showed high resolution, and PET imaging enabled quantification and confirmation of the specificity. In conclusion, we have successfully developed the specific PSMA-targeting IO nanoparticle, DOTA-IO-GUL, as a dual-modality probe for complementary PET/MR imaging. From the Clinical EditorThe combination of using Positron Emission Tomography (PET) and computed tomography (CT) in clinical practice is now the norm. With advances in technology, the next step would be to develop combined PET and Magnetic Resonance (MR) dual-imaging. In this article, the authors described their positive study on the development of a dual-modal PET/MR imaging probe using a prostate cancer model.

Bio-functionalized water-soluble ZnS quantum dots using carboxymethylchitosan

The major goal of this study was to develop an innovative green route for synthesizing biocompatible water-soluble luminescent QDs using chemically modified chitosan as the ligand in aqueous media. The preparation of ZnS QDs bio-functionalized by carboxymethylchitosan (CMC) was performed using a single-step aqueous colloidal process at room temperature. The results showed that water-dispersible ZnS nanocrystals capped by CMC were produced within the quantum-size confinement regime. Moreover, the luminescent properties of ZnS QDs were significantly affected by the pH during the synthesis due to the size distribution of the nanoparticles and their density of surface states.

Green and facile synthesis of water-soluble ZnS quantum dots nanohybrids using chitosan derivative ligands

Semiconductor quantum dots (QDs) are fluorescent nanocrystals with great potential for use in biomedical and environmental applications. However, eliminating the potential cytotoxicity of the QDs comprised of a core containing heavy metals and using a green chemical process are still challenges faced by the research community. Thus, the aim of this work was to develop a novel green and facile route for synthesizing biocompatible water-soluble QDs using chemically modified chitosan as a capping ligand in aqueous media, with their chemical and optical properties tuned by the nanoparticle size. The synthesis of ZnS QDs capped by carboxymethylchitosan (CMC) was performed using a single-step aqueous colloidal process at room temperature. The nanohybrids were extensively characterized by several imaging and spectroscopic techniques, and the results demonstrated that ultra-small ZnS nanocrystals were produced with average nanoparticles ranging from 3.2 to 4.2 nm. In addition, the luminescent properties of ZnS QDs were influenced by the pH during the synthesis due to the size distribution of the nanoparticles produced. Hence, new “heavy metal free” nanohybrids were successfully developed based on ZnS QDs directly surface-functionalized by biopolymer exhibiting fluorescent activity that may be potentially used in a large number of eco-friendly and biomedical applications.