ZnCl2 Complexes Research Articles

Structural and spectroscopic characterization of N1,N2-diphenylacenapthylene-1,2-diimines and the influence of substituents on the viscosity of alkyl magnesium solutions

Butyl octyl magnesium solutions are important raw materials in various chemical processes but suffer from their high reactivity with even traces of water, protic solvents or oxygen and an increased viscosity in hydrocarbon solution due to the formation of polymeric structures. N1,N2-diphenylacenaphthylene-1,2-diimines (BIANs) have already been identified as potential candidates to reduce the viscosity of alkyl magnesium solutions and this study provides a systematic insight into the dependence of this ability on the position and structures of substituents on the BIAN. Besides the various BIANs, ZnCl2 complexes and hydrogenated derivatives were characterized and tested for their ability to reduce the viscosity. HPLC-high resolution mass spectrometry, MALDI-ToF mass spectrometry, but most important FTIR and NMR experiments under inert conditions have been used to shine light on the interaction of the different BIAN derivatives with alkyl magnesium solutions. Hydrogenated BIANs, especially those with bulky alkyl groups in the ortho position(s) have been identified as the most promising candidates. An additional benefit of the hydrogenated species is that in contrast to BIANs and BIAN-Zn complexes they do not undergo permanent chemical modification and can be reused after extraction.

Enhanced Thermally Activated Delayed Fluorescence by Sole Coordination: From an Organic Molecule to Its Zinc Complex.

A BPAPTPyC organic molecule containing a sandwich structural chromophore is designed and synthesized to produce blue thermally activated delayed fluorescence (TADF). The chromophore is composed of two di(4-tert-butylphenyl)amino donors and one inserted terpyridyl acceptor hitched at positions 1, 8, and 9 of a single carbazole via the p-phenylene group, in which the multiple space π-π interactions between the donor and acceptor enable the molecule to possess the TADF feature with a high energy emission at 470 nm but a low photoluminescence quantum yield (PLQY) and a small proportion of the delayed component. In contrast, the corresponding Zn(BPAPTPyC)Cl2 complex has a high PLQY and a short lifetime with a red-shifted emission due to the enhanced rigidity and electron accepting ability of the terpyridyl group from coordination. A solution-processed organic light-emitting diode (OLED) based on the complex achieves a maximum external quantum efficiency (EQE) of 17.9% with an emission peak at 585 nm, while an OLED of the organic molecule produces blue emission with a maximum EQE of 2.7%.

Novel Complex of Zinc (II) Dichloroethylenediamine: Synthesis, Characterization, In-silico, and In-vitro Evaluation against Cervical Cancer Cells.

Cervical cancer is a malignancy originating from the cervix and often caused by oncogenic Human Papilloma Virus (HPV), specifically subtypes 16 and 18. Anticancer drugs are chemotherapeutic compounds used for cancer treatment. Therefore, this research aims to synthesize and characterize Zinc (II) dichloroethylenediamine (Zn(en)Cl2) complex, as well as determine its antiproliferative activity against HeLa cells. The Zn(en)Cl2 complex was successfully synthesized, and the antiproliferative activity was tested. The synthesis involved reacting ethylenediamine and KCl with Zn metal. The complex formed was characterized using a conductometer, UV-Vis spectroscopy, FT-IR spectroscopy, and XRD, while the activity was measured against HeLa cells. The synthesis yielded a 56.12% conversion with a melting point of 198-200 oC and a conductivity value of 2.02 mS/cm. The Zn(en)Cl2 complex showed potential activity against HeLa cells with an IC50 value of 898.35 µg/mL, which was evidenced by changes in the morphological structure of HeLa cells. Its interaction with DNA targets was investigated by employing molecular docking. The observed data indicated that the Zn(en)Cl2 complex bound to DNA at the nitrogenous base Guanine (DG) by coordinate covalent bonds. Interestingly, DG maintained interaction with the complex until the end of the docking simulation. Additionally, molecular dynamics (MD) simulation was conducted, and the results showed that Zn(en)Cl2 remained bound to the DNA binding pocket all through the process.

Aggregation‐Induced Emission in a Flexible Phosphine Oxide and its Zn(II) Complexes—A Simple Approach to Blue Luminescent Materials

AbstractEasily accessible blue‐emitting materials are in the focus of ongoing research, as they still lack the efficiency and lifetime of their red and green counterparts. The new multidentate phosphine oxide ligands and two respective ZnCl2 complexes presented here combine a straightforward synthesis with high yields and show interesting luminescent properties. The free ligand exhibits blue luminescence in the crystalline state, but not in amorphous films or diluted solution. In contrast, the Zn(II) complexes shows intense blue luminescence in the crystalline state as well as in amorphous thin films and in solution. Fluorescence lifetime imaging microscopy measurements show luminescence lifetimes of 3–6 ns indicative of fluorescence. By combining the experimental data with quantum chemical calculations, we propose a model where the conformation of the molecule is restricted, either via the crystal environment, aggregation, or the steric fixation by the coordinating central atom, blocking the nonradiative relaxation from the excited into the ground electronic state. However, this nonradiative relaxation is still possible in the gas phase via elongation of a PC bond. These results may provide a general mechanism to explain the luminescence properties in a whole class of organic phosphine oxides.

Preparation, Characterization and Antimicrobial Activity of Pd(II), Zn(II) and Cu(II) Complexes of Benzimidazoles and Schiff Bases Including Ferrocene Group

PdCl2, ZnCl2 and CuCl2 complexes of three benzimidazole derivatives and two Schiff bases having the ferrocene group were synthesized and characterized. It was unexpectedly noticed that the Pd(II) and Zn(II) complexes exhibit paramagnetic characters corresponding to about one electron caused by the ferrocene moiety. For the same reason, the magnetic moment value of the Cu(II) complexes was also higher than the anticipated values. Besides, the antimicrobial activity of the complexes was investigated against six bacteria and three fungi. Comparing the ligands, the Schiff bases exhibited higher antimicrobial activity than the benzimidazole derivatives, especially on Gram+ bacteria. Among all compounds investigated in this work, [Zn(SB1)2]·2H2O showed the highest activity against S. epidermidis and S. aureus which are Gram+ bacteria.

Synthesis, Structural Characterization, and Guest Exchange Properties of Hydrogen-Bonded Organic Frameworks Based on Bis(benzimidazole)ZnCl2 Complexes.

Hydrogen-bonded organic frameworks (HOFs) based on coordination compounds constitute a developing class of interesting porous materials. Herein, we report on the synthesis, crystal structures, and guest exchange properties of four HOFs based on zinc dichlorido complexes that bear a bis(benzimidazolyl)methane ligand (bis(benzimidazole)ZnCl2). The porous structures of these bis(benzimidazole)ZnCl2-based HOFs are characterized predominantly by intermolecular N-H···Cl hydrogen bonds in conjunction with π-π interactions. One of these HOFs was found to exchange guest molecules via single-crystal-to-single-crystal transformations with or without structural change. A single-crystal X-ray diffraction study revealed that the guest exchange accompanied by a structural change is induced by the cleavage of the N-H···Cl hydrogen bonds between the bis(benzimidazole)ZnCl2 complexes, followed by the formation of alternate hydrogen bonds with guest molecules. This result suggests that the use of weaker N-H···Cl hydrogen bonds than those typically used for the construction of HOFs (e.g., carboxylic acid dimers, N-heterocycles, and charge-assisted moieties) may represent a convenient strategy to synthesize flexible HOFs.

A Redox-Active Tetrazine-Based Pincer Ligand for the Reduction of N-Oxyanions Using a Redox-Inert Metal.

The reaction chemistry of the bis-tetrazinyl pyridine ligand (btzp) towards nitrogen oxyanions coordinated to zinc is studied in order to explore the reduction of the NOx - substrates with a redox-active ligand in the absence of redox activity at the metal. Following syntheses and characterization of (btzp)ZnX2 for X=Cl, NO3 and NO2 , featuring O-Zn linkage of both nitrogen oxyanions, it is shown that a silylating agent selectively delivers silyl substituents to tetrazine nitrogens, without reductive deoxygenation of NOx -1 . A new synthesis of the highly hydrogenated H4 btzp, containing two dihydrotetrazine reductants is described as is the synthesis and characterization of (H4 btzp)ZnX2 for X=Cl and NO3 , both of which show considerable hydrogen bonding potential of the dihydrotetrazine ring NH groups. The (H4 btzp)ZnCl2 complex does not bind zinc in the pincer pocket, but instead H4 btzp becomes a bridge between neighboring atoms through tetrazine nitrogen atoms, forming a polymeric chain. The reaction of AgNO2 with (H4 btzp)ZnCl2 is shown to proceed with fast nitrite deoxygenation, yielding water and free NO. Half of the H4 btzp reducing equivalents form Ag0 and thus the chloride ligand remains coordinated to the zinc metal center to yield (btzp)ZnCl2 . To compare with AgNO2 , experiments of (H4 btzp)ZnCl2 with NaNO2 result in salt metathesis between chloride and nitrite, highlighting the importance of a redox-active cation in the reduction of nitrite to NO.

Molecular and Crystal Structure of a Chitosan-Zinc Chloride Complex.

We determined the molecular and packing structure of a chitosan–ZnCl2 complex by X-ray diffraction and linked-atom least-squares. Eight D-glucosamine residues—composed of four chitosan chains with two-fold helical symmetry, and four ZnCl2 molecules—were packed in a rectangular unit cell with dimensions a = 1.1677 nm, b = 1.7991 nm, and c = 1.0307 nm (where c is the fiber axis). We performed exhaustive structure searches by examining all of the possible chain packing modes. We also comprehensively searched the positions and spatial orientations of the ZnCl2 molecules. Chitosan chains of antiparallel polarity formed zigzag-shaped chain sheets, where N2···O6, N2···N2, and O6···O6 intermolecular hydrogen bonds connected the neighboring chains. We further refined the packing positions of the ZnCl2 molecules by theoretical calculations of the crystal models, which suggested a possible coordination scheme of Zn(II) with an O6 atom.

Synthesis, structural characterization and antimicrobial activity of Schiff bases and benzimidazole derivatives and their complexes with CoCl2, PdCl2, CuCl2 and ZnCl2

In this study, new Schiff bases (H2L1 and H2L2) and benzimidazolylphenol derivatives (HL3 − HL5) derived from 5-chlorosalicylaldehyde and appropriate aminophenol and o-phenylenediamine derivatives including 4-methyl/4,5-dimethyl/4-chloro‑5-nitro groups were synthesized and characterized. CoCl2, PdCl2, CuCl2 and ZnCl2 complexes of the ligands were synthesized and characterized by using elemental analysis, molar conductivity, magnetic moment, FT-IR and NMR spectroscopy. In addition, the crystal structure of H2L1 and [Pd(L1)(CH3CN)]·H2O were determined by X-ray diffraction spectroscopy. Keto-enol tautomerism is observed in the Schiff base compounds according to spectral data. Antimicrobial activities of the compounds were tested toward six bacteria and three fungi. Some metal complexes (e.g. Co(II) complexes of the benzimidazole derivatives) showed higher activity towards the test microorganisms than the ligands. In addition, it is observed that the Co(II) complexes show in a wide range antimicrobial activity compared to the other complexes.

Synthesis, Characterization and Antimicrobial Activity of Schiff Bases Including Three Hydroxy Groups and Their CoCl2, PdCl2, CuCl2 and ZnCl2 Complexes

AbstractFour Schiff bases, (3/4/2/4)‐{[(2‐hydroxy‐5‐methylphenyl)imino]methyl}benzene‐1,2/1,3/1,4/1,2‐diols (H3L1‐H3L4), derived from 2,3/2,4/2,5/3,4‐dihydroxybenzaldehydes and 2‐amino‐4‐methylphenol, and their CoCl2, PdCl2, CuCl2 and ZnCl2 complexes were synthesized and characterized. The structures of the complexes were suggested on the basis of elemental analysis, TGA, molar conductivity, magnetic moment, FT‐IR, UV‐vis and NMR spectroscopy. According to the analytical and spectral data, the ligands H3L1, H3L2 and H3L3 acted as tridentate, giving chelate structures in the complexes, via the C=N nitrogen and two phenolate oxygen atoms whereas H3L4 acted as bidentate. In addition, the crystal structure of H3L1 was determined by X‐ray diffraction. The spectral data show that there is keto‐enol tautomerization in the ligands and keto form is dominant in H3L1 and H3L3 while enol form is in H3L2 and H3L4. Antimicrobial activities of the compounds were tested against six bacteria and three fungi. [Zn(H2L1)Cl]⋅4H2O showed superior activity toward the fungi C. albicans, C. parapsilosis and C. tropicalis compared to H3L1 and the other compounds. Strong activity of H3L1, H3L2 and H3L3 was observed toward S. aureus whereas they showed weak activity to the other microorganisms.

An effective non-chromatographic method for the purification of phenanthrolines and related ligands

1,10-Phenanthrolines are widely employed as ligands, but their use on a large scale is constrained by their difficult purification, which usually requires lengthy chromatographic separations. Herein, we describe a purification strategy that takes advantage of the high stability and low solubility of phenanthroline complexes to separate them from the by products of their synthesis. The formation of ZnCl2 complexes was employed, from which the free ligand can be recovered by reaction with aqueous NH3 in a biphasic CH2Cl2/H2O system. The same strategy was also successfully employed to purify related quinolino-guanidine ligands, demonstrating that the procedure is of general applicability.

Aqueous ZnCl2 Complex Catalyzed Prins Reaction of Silyl Glyoxylates: Access to Functionalized Tertiary α-Silyl Alcohols.

An efficient Prins reaction of silyl glyoxylates in the presence of an aqueous ZnCl2 complex as a catalyst was developed, providing functionalized tertiary α-silyl alcohols in high yields under mild conditions. A preliminary investigation indicated that the aqueous ZnCl2 complex acted as a dual functional catalyst of Brønsted and Lewis acid to activate the carbonyl groups of silyl glyoxylates via a dual-activation model.

A diamino-substituted carbodiphosphorane as strong C-donor and weak N-donor: isolation of monomeric trigonal-planar L·ZnCl2.

The isolation, structural characterization and coordination chemistry of a di(amino)-substituted carbodiphosphorane (CDP) are reported. Compared to the analogue, dianionic bis(iminophosphoryl)methandiides, the CDP is a stronger C-, but much weaker N-donor which led to the isolation of solely C-coordinated metal complexes amongst an unusual monomeric trigonal-planar L·ZnCl2 complex.

Zinc(II) Terpyridine Complexes: Substituent Effect on Photoluminescence, Antiproliferative Activity, and DNA Interaction.

A series of ZnCl2 complexes (compounds 1–10) with 4′-(substituted-phenyl)-2,2′:6′,2′′-terpyridine that bears hydrogen (L1), p-methyl (L2), p-methoxy (L3), p-phenyl (L4), p-tolyl (L5), p-hydroxyl (L6), m-hydroxyl (L7), o-hydroxyl (L8), p-carboxyl (L9), or p-methylsulfonyl (L10) were prepared and then characterized by 1H NMR, electrospray mass-spectra (ESI-MS), IR, elemental analysis, and single crystal X-ray diffraction. In vitro cytotoxicity assay was used to monitor the antiproliferative activities against tumor cells. Absorption spectroscopy, fluorescence titration, circular dichroism spectroscopy, and molecular modeling studied the DNA interactions. All of the compounds display interesting photoluminescent properties and different maximal emission peaks due to the difference of the substituent groups. The cell viability studies indicate that the compounds have excellent antiproliferative activity against four human carcinoma cell lines, A549, Bel-7402, MCF-7, and Eca-109, with the lowest IC50 values of 0.33 (10), 0.66 (6), 0.37 (7), and 1.05 (7) μM, respectively. The spectrophotometric results reveal that the compounds have strong affinity binding with DNA as intercalator and induce DNA conformational transition. Molecular docking studies indicate that the binding is contributed by the π…π stacking and hydrogen bonds, providing an order of nucleotide sequence binding selectivity as ATGC > ATAT > GCGC. These compounds intercalate into the base pairs of the DNA of the tumor cells to affect their replication and transcription, and the process is supposed to play an important role in the anticancer mechanism.

Structures, Phase Behavior, and Fluorescent Properties of 3-Phenyl-1-(pyridin-2-yl)-1H-pyrazol-5-amine and Its ZnCl2 Complex.

The synthesis of the asymmetric ligand 3-phenyl-1-(pyridin-2-yl)-1H-pyrazol-5-amine (L1) and its single-crystal X-ray structure are reported. L1 displays crystallographic symmetry (orthorhombic, Pccn) higher than its molecular symmetry (point group C1) and also displays supercooling, with a difference in the melting and solidification points of over 100 °C. Upon complexation with ZnCl2, L1 engages in both primary cation and secondary anion coordination via hydrogen bonding, and the complex exhibits a room-to-low-temperature single crystal-to-crystal phase transition. The ZnCl2 complex becomes a birefringent fluid mixed with crystalline domains at high temperatures, as detected by polarized optical microscopy. Examination of the photoluminescence properties showed that the emission intensity increased and a pronounced bathochromic shift was observed in the emission maximum upon going from solution to the solid state, for both the ligand and complex, consistent with aggregation-induced emission behavior.

Germylene stabilized group 12 metal complexes and their reactivity with chalcogens.

This manuscript reports the first examples of germylene stabilized cadmium complexes {[{(i-Bu)2ATIGe(i-Pr)}2(CdI2)] (3, monomeric), [{(i-Bu)2ATIGe(i-Pr)(CdCl2)}2] (6, dimeric), [{(i-Bu)2ATIGe(i-Pr)(CdI2)}2] (7, dimeric)} and novel germylene zinc complexes {[{(i-Bu)2ATIGe(i-Pr)}2(ZnCl2)] (2, monomeric), [{(i-Bu)2ATIGe(i-Pr)(ZnI2)}2] (5, dimeric)} (ATI = aminotroponiminate). The reactions of germylene zinc complex [{(i-Bu)2ATIGe(i-Pr)(ZnCl2)}2] (4) with elemental sulphur and selenium resulted in the first examples of germathione and germaselenone stabilized ZnCl2 complexes [{(i-Bu)2ATIGe(i-Pr)(S)(ZnCl2)}2] (8) and [{(i-Bu)2ATIGe(i-Pr)(Se)(ZnCl2)}2] (9), respectively. Compound 4 was obtained through the reaction of compound 2 with ZnCl2. Interconversions between the monomeric and dimeric zinc/cadmium complexes (2 ↔ 4/3 ↔ 7) are shown. Compounds 2-3 and 5-9 are characterized by multinuclear NMR spectroscopy and single crystal X-ray diffraction studies are performed on compounds 2-3, 5-7, and 9. To understand the nature of bonding in the first examples of germylene cadmium complexes, ab initio calculations are also carried out on compounds 3 and 7.

Spray-chilling encapsulation of 2-acetyl-1-pyrroline zinc chloride using hydrophobic materials: Storage stability and flavor application in food

2-Acetyl-1-pyrroline (2AP) is a popular yet highly unstable aroma compound, which limits its commercial use as a flavoring ingredient. The stability and application of spray-chilled paraffin-coated microcapsules of 2AP zinc chloride complex (2AP–ZnCl2) were investigated in this study. 2AP–ZnCl2 microcapsules (0.081% (w/w) 2AP loading) and unprotected 2AP–ZnCl2 complex were subjected to ambient storage at four different relative humidities (RH; ∼0%, ∼22.5%, ∼43.2% and ∼100%). The results showed that the microcapsules had significantly greater 2AP stability compared with the unprotected complex under all storage conditions studied. A flavor application study using instant rice was also performed to validate the potential effectiveness of using 2AP–ZnCl2 microcapsules as a flavoring agent. Full 2AP recovery was achieved after the cooking process, where the controlled release function of the microcapsules was clearly exhibited. The results demonstrated that microencapsulation of 2AP–ZnCl2 allows for more flexible handling/storage practices and has potential for application by the flavor industry.

ChemInform Abstract: Zinc Catalyzed Guanylation Reaction of Amines with Carbodiimides/Isocyanate Leading to Guanidines/Urea Derivatives Formation.

We report the highly chemo-selective catalytic addition of N–H bonds from various aromatic amines to carbodiimides and isocyanates using (Ar-BIAO)ZnCl2 complexes [Ar-BIAO = N-(aryl)imino-acenapthenone, Ar = 2,6-Me2C6H3 (1), 2,4,6 Me3C6H2 (2), 2,6-iPr2C6H3 (3)] as the pre-catalyst to prepare guanidine and urea derivatives in 55-90% yield. The complex 3 showed higher catalytic activity than analogous complexes 1 and 2 under similar reaction conditions. The catalytic guanylation of N–H bonds with heterocumulenes displays a broad substrate scope. The amines having electron donating groups underwent higher conversion than the amines having electron withdrawing groups to afford corresponding guanidine or urea derivatives. A possible mechanism involving penta-coordinated zinc transition state for the catalytic reaction is presented.

Zinc catalyzed Guanylation reaction of Amines with Carbodiimides/ Isocyanate leading to Guanidines/Urea derivatives formation

We report the highly chemo-selective catalytic addition of N–H bonds from various aromatic amines to carbodiimides and isocyanates using (Ar-BIAO)ZnCl2 complexes [Ar-BIAO = N-(aryl)imino-acenapthenone, Ar = 2,6-Me2C6H3 (1), 2,4,6 Me3C6H2 (2), 2,6-iPr2C6H3 (3)] as the pre-catalyst to prepare guanidine and urea derivatives in 55-90% yield. The complex 3 showed higher catalytic activity than analogous complexes 1 and 2 under similar reaction conditions. The catalytic guanylation of N–H bonds with heterocumulenes displays a broad substrate scope. The amines having electron donating groups underwent higher conversion than the amines having electron withdrawing groups to afford corresponding guanidine or urea derivatives. A possible mechanism involving penta-coordinated zinc transition state for the catalytic reaction is presented. We report the highly chemo-selective catalytic addition of N–H bonds from various aromatic amines to carbodiimides and isocyanates using (Ar-BIAO)ZnCl2 complex [Ar-BIAO = N-(2,6-diisopropylphenyl)imino-acenapthenone, (3)] as the pre-catalyst to prepare guanidine and urea derivatives in 53-90% and 79-95% yield, respectively.

Chalcogenated (S)-(−)-nicotine derivatives as chiral linkers for 1D coordination polymers

Reactions of zinc(II) chloride with (S)-(−)-nicotine (Nic), cotinine, thionicotine and selenonicotine in 1:1molar ratio yielded new metal complexes, which were characterized by elemental analysis, infrared, 13C and 1H NMR spectral methods. Single crystal X-ray diffraction studies of ZnCl2 complexes with thionicotine and selenonicotine revealed that the two complexes form isostructural crystals build of 1D coordination polymers (CP) and that coordination to metal centers alters the conformation of the parent organic ligand from syn to anti. Quantum chemical calculations indicate that in the isolated state the anti conformation of the uncoordinated chalcogen nicotine lactams is slightly more preferred energetically and it does not undergo substantial changes upon coordination to the metal center. The preference for the syn conformation in crystals of thio- and selenolactams of nicotine might be ascribed to their involvement in columnar stacking interactions, which do not operate in the isolated state and are also absent in crystals of their adducts with ZnCl2. This study has provided useful information regarding functionalization of (S)-(−)-nicotine molecule as a mixed-donor-atom ligand to enforce formation of 1D coordination polymers.