Complexes 1b Research Articles

CuAAC "Click"-Derived Luminescent 2-(2-(4-(4-(Pyridin-2-yl)-1H-1,2,3-triazol-1-yl)butoxy)phenyl)benzo[d]thiazole-Based Ru(II)/Ir(III)/Re(I) Complexes as Anticancer Agents.

To enhance the cytoselective behavior of the complexes, we intended to develop a CuAAC "click"-derived synthetic protocol for the preparation of 2-(2-(4-(4-(pyridin-2-yl)-1H-1,2,3-triazol-1-yl)butoxy)phenyl)benzo[d]thiazole-based Ru(II)/Ir(III)/Re(I) complexes, and their cytotoxicity against three different cancer cell lines (MCF-7, HeLa, and U87MG) in consort with one normal cell line (HEK-293) was evaluated. In our detailed investigations, the significant cytotoxic nature of the Ru(II) complex 7a compared to Ir(III) and Re(I) complexes (7b and 7c, respectively) was observed. Complex 7a was capable of MCF-7 cell apoptosis via the inhibition of both S- and G2/M-phase cell cycle arrest in association with a substantial quantity of ROS production and DNA intercalation.

Facile synthesis of InIII-salen complexes from indium metal and their use as catalysts for the chemical fixation of carbon dioxide in mild conditions

An alternative, very simple and improved route to obtain indium(III) tetrahaloindate salts of tetrabutylammonium (TBA)[InX4] – 1a (X = Cl), 1b (X = Br) and 1c (X = I) – in high yields (74 – 82%) was developed. Indium(III) tetrahaloindates were then used as starting materials for the synthesis of In(salen)X complexes 2a (X = Cl, 88%), 2b (X = Br, 94%) and 2c (X = I, 88%). Compounds 2a-c were characterized by FT-IR, Raman, and 1H and 13C NMR spectroscopies. The In-salen complexes were able to promote the CO2 cycloaddition reaction with styrene oxide in mild and solvent-free conditions; complex 2a presented the best performance in the initial screening, achieving quantitative conversion (>99%). The parameters of the catalytic system were optimized, and a series of epoxides were tested as substrates for the production of cyclic carbonates with conversions varying from 38% to quantitative. The present study provides a simple method to cheaply and easily prepare indium(III) complexes and employ them to produce value-added chemicals from CO2.

Co-condensation with photoexcited cryptochromes facilitates MAC3A to positively control hypocotyl growth in Arabidopsis.

Cryptochromes (CRYs) are blue light receptors that mediate plant photoresponses through regulating gene expressions. We recently reported that Arabidopsis CRY2 could form light-elicited liquid condensates to control RNA methylation. However, whether CRY2 condensation is involved in other gene expression-regulatory processes remains unclear. Here, we show that MOS4-associated complex subunits 3A and 3B (MAC3A/3B) are CRY-interacting proteins and assembled into nuclear CRY condensates. mac3a3b double mutants exhibit hypersensitive photoinhibition of hypocotyl elongation, suggesting that MAC3A/3B positively control hypocotyl growth. We demonstrate the noncanonical activity of MAC3A as a DNA binding protein that modulates transcription. Genome-wide mapping of MAC3A-binding sites reveals that blue light enhances the association of MAC3A with its DNA targets, which requires CRYs. Further evidence indicates that MAC3A and ELONGATED HYPOCOTYL 5 (HY5) occupy overlapping genomic regions and compete for the same targets. These results argue that photocondensation of CRYs fine-tunes light-responsive hypocotyl growth by balancing the opposed effects of HY5 and MAC3A.

Self-Assembly and Photothermal Conversion of MetallaRussian Doll and Metalla[2]catenanes Induced via Multiple Stacking Interactions.

A variety of organometallic supramolecular architectures have been constructed over the past decades and their properties were also explored via different strategies. However, the synthesis of metalla-Russian doll is still a fascinating challenge. Herein, a series of new coordination supramolecular complexes, including a metalla-Russian doll, metalla[2]catenanes, and metallarectangles, were synthesized by using meticulously selected Cp*Rh (Cp* = η5-C5Me5) building units (E1, E2, and E3) and three rigid anthracylpyridine ligands (L1, L2, and L3) via a self-assembly strategy. While the combination of the short ligand L1 and E1 or E2 generated two metallarectangles, the longer ligand L2 containing an alkynyl group resulted in two new [2]catenanes, most likely due to which the strong electron-donating effect of alkynyl groups causes self-accumulation. Interestingly, an unusual Russian doll assembly was obtained through the reaction of L3 and E3 based on sextuple π···π stacking interactions. Furthermore, the dynamic structural conversion between [2]catenanes and the corresponding metallarectangles could be observed through concentration-, solvent-, and guest-induced effects. The [2]catenane complexes 4b displayed efficient photothermal conversion efficiency in solution (20.2%), in comparison with other organometallic macrocycles. We believe that π···π stacking interactions generate active nonradiative pathways and promote radiative photodeactivation pathways. This study proves the versatility of half-sandwich building units, not only to build complicated supramolecular topologies but also in effective functional materials for various appealing applications.

A Series of New Manganese(II) Polynuclear Complexes Based on Nitrothiacalix[4]arenes: The Study of Interplay between Macrocycle Platform Flexibility and Structural Diversity of Coordination Compounds

Four new manganese(II) complexes, based on dinitro and tetranitrothiacalix[4]arenes, were synthesized and characterized from structural points of view in the crystalline phase. It was revealed that thiacalix[4]arenes decorated with two and four electron withdrawing groups, when combined with MnCl2, afforded the formation of similar tetranuclear complexes 1 and 2a with two non-equivalent metal ions and a rhombic geometry of the metallic cluster core. The distortion of the coordination sphere of metal cations within the obtained complexes was found to be dependent on the number of nitro groups located at the upper rim of the macrocyclic backbone, adopted in cone conformation. The tetranuclear complex 2b of a different type, displaying the formation of a dinuclear cluster core, crystallized in a non-centrosymmetric space group was obtained, when tetranitrothiacalix[4]arene, adopted in a partial cone conformation, was involved in coordination with manganese(II) cations. The switching of coordination behavior for the macrocyclic ligand in 2b was achieved due to the presence of upper-rim-disposed electron-withdrawing nitro groups, increasing the flexibility of the macrocyclic backbone by breaking the H-bonding between the OH phenolate moieties within the ligand structure. Finally, the use of 2,2′-bipyridine as an auxiliary ligand in coordination with tetranitrothiacalix[4]arene and manganese(II) cations led to the third type complex formation 3, where the macrocycle platform adopted in a 1.2-alternate conformation.

Iodine(I) and Silver(I) Complexes Incorporating 3-Substituted Pyridines.

Building upon the first report of a 3-acetaminopyridine-based iodine(I) complex (1b) and its unexpected reactivity toward tBuOMe, several new 3-substituted iodine(I) complexes (2b-5b) have been synthesized. The iodine(I) complexes were synthesized from their analogous silver(I) complexes (2a-5a) via a silver(I) to iodine(I) cation exchange reaction, incorporating functionally related substituents as 3-acetaminopyridine in 1b; 3-acetylpyridine (3-Acpy; 2), 3-aminopyridine (3-NH2py; 3), and 3-dimethylaminopyridine (3-NMe2py; 4), as well as the strongly electron-withdrawing 3-cyanopyridine (3-CNpy; 5), to probe the possible limitations of iodine(I) complex formation. The individual properties of these rare examples of iodine(I) complexes incorporating 3-substituted pyridines are also compared to each other and contrasted to their 4-substituted counterparts which are more prevalent in the literature. While the reactivity of 1b toward etheric solvents could not be reproduced in any of the functionally related analogues synthesized herein, the reactivity of 1b was further expanded to a second etheric solvent. Reaction of bis(3-acetaminopyridine)iodine(I) (1b) and iPr2O gave [3-acetamido-1-(3-iodo-2-methylpentan-2-yl)pyridin-1-ium]PF6 (1d), which demonstrated potentially useful C-C and C-I bond formation under ambient conditions.

Germylene-Fe complexes caused by heterometallic coupling and investigation into the 3d-4p bonding

The interpretation of heterometallic bonding nature is a basic work of inorganic chemistry. By means of intermetallic substitution of germylene anions with iron halide complexes CpFe(CO)2I and β-diketiminato FeII chloride, the ferrogermylene complexes 3a, 3b and 4a were synthesized and structurally characterized. The structural and IR characterizations show the presence of the Ge←Fe π backbonding in molecules 3a, 3b and 4a. The computational works on frontier molecular orbitals and their comparison of energy states confirmed that σ donation and π backbonding are both weak in these molecules, despite three complexes have longer Ge-Fe bonds, whose strength decreases slightly with the degressive electron density around Fe environment in a sequence from 3a, 3b to 4a.

Synthesis, characterization, crystal structure, Hirshfeld surface analysis of Cd(II)-1, 2-benzisothiazol-3(2H)-one complexes

Reaction of [Cd(OAc)2].2H2O with Nabit (Hbit=1, 2-benzisothiazol-3(2H)-one) afford [Cd(bit)2]. Treatment of [Cd(bit)2] with the diamines ligands (L'); ethylenediamine (en), 1,10-phenanthroline (phen) or 2,2′-bipyridine (bipy) afford complexes of the type [Cd(bit)2(L')]. X-ray crystal structure analysis of [Cd(bit)2(bipy)] showed that it is a mixture of the two binuclear complexes; [Cd(bipy)(κ1-bit)(μ-bit)]2(2a) and [Cd2(bipy)2(κ1-bit)4(H2O)2(μ-H2O)] (2b). Each cadmium atom is peta coordinated in complex 2a whereas hexa coordinated in complex 2b. The coordination geometry is distorted square pyramidal and distorted octahedral in complex 2a and 2b, respectively. The crystal packing of complex 2a is stabilized by CH⋯O and π⋯π stacking interactions whereas the crystal packing of complex 2b is stabilized by OH⋯O, CH⋯O and π⋯π stacking interactions. The intermolecular interactions in both complexes are further inspected by Hirshfeld surface analysis. The void analysis is carried out to check the presence or absence of the large cavity in complex 2a and 2b.

Synthesis and Characterisation of Fluorescent Novel Pt(II) Cyclometallated Complexes with Anticancer Activity.

Cancer poses a significant threat to global health and new treatments are required to improve the prognosis for patients. Previously, unconventional platinum complexes designed to incorporate polypyridyl ligands paired with diaminocyclohexane have demonstrated anticancer activity in KRAS mutated cells, previously thought to be undruggable and have cytotoxicity values up to 100 times better than cisplatin. In this work, these complexes were used as inspiration to design six novel cyclometallated examples, whose fluorescence could be exploited to better understand the mechanism of action of these kinds of platinum drugs. The cytotoxicity results revealed that these cyclometallated complexes (CMCs) have significantly different activity compared to the complexes that inspired them; they are as cytotoxic as cisplatin and have much higher selectivity indices in breast cancer cell lines (MCF10A/MCF-7). Complexes 1b, 2a, and 3b all had very high selectivity indexes compared to previous Pt(II) complexes. This prompted further investigation into their DNA binding properties, which revealed that they had good affinity to ctDNA, especially CMCs 1a and 3b. Their inherent fluorescence was successfully utilised in the calculation of their DNA binding affinity and could be useful in future work.

Evaluating the inhibitory activity of ferrocenyl Schiff bases derivatives on 5-lipoxygenase: Computational and biological studies

In the search for new 5-LOX inhibitors, two ferrocenyl Schiff base complexes functionalized with catechol ((ƞ5-(E)-C5H4-NCH-3,4-benzodiol)Fe(ƞ5-C5H5) (3a)) and vanillin ((ƞ5-(E)-C5H4-NCH-3-methoxy-4-phenol)Fe(ƞ5-C5H5) (3b)) were obtained. Complexes 3a and 3b were biologically evaluated as 5-LOX inhibitors showed potent inhibition compared to their organic analogs (2a and 2b) and known commercial inhibitors, with IC50 = 0.17 ± 0.05 μM for (3a) and 0.73 ± 0.06 μM for (3b) demonstrated a highly inhibitory and potent effect against 5-LOX due to the incorporation of the ferrocenyl fragment. Molecular dynamic studies showed a preferential orientation of the ferrocenyl fragment toward the non-heme iron of 5-LOX, which, together with electrochemical and in-vitro studies, allowed us to propose a competitive redox deactivation mechanism mediated by water, where Fe(III)-enzyme can be reduced by the ferrocenyl fragment. An Epa/IC50 relationship was observed, and the stability of the Schiff bases was evaluated by SWV in the biological medium, observing that the hydrolysis does not affect the high potency of the complexes, making them interesting alternatives for pharmacological applications.

Ruthenium Complexes with Protic Ligands: Influence of the Position of OH Groups and π Expansion on Luminescence and Photocytotoxicity

Protic ruthenium complexes using the dihydroxybipyridine (dhbp) ligand combined with a spectator ligand (N,N = bpy, phen, dop, Bphen) have been studied for their potential activity vs. cancer cells and their photophysical luminescent properties. These complexes vary in the extent of π expansion and the use of proximal (6,6'-dhbp) or distal (4,4'-dhbp) hydroxy groups. Eight complexes are studied herein as the acidic (OH bearing) form, [(N,N)2Ru(n,n'-dhbp)]Cl2, or as the doubly deprotonated (O- bearing) form. Thus, the presence of these two protonation states gives 16 complexes that have been isolated and studied. Complex 7A, [(dop)2Ru(4,4'-dhbp)]Cl2, has been recently synthesized and characterized spectroscopically and by X-ray crystallography. The deprotonated forms of three complexes are also reported herein for the first time. The other complexes studied have been synthesized previously. Three complexes are light-activated and exhibit photocytotoxicity. The log(Do/w) values of the complexes are used herein to correlate photocytotoxicity with improved cellular uptake. For Ru complexes 1-4 bearing the 6,6'-dhbp ligand, photoluminescence studies (all in deaerated acetonitrile) have revealed that steric strain leads to photodissociation which tends to reduce photoluminescent lifetimes and quantum yields in both protonation states. For Ru complexes 5-8 bearing the 4,4'-dhbp ligand, the deprotonated Ru complexes (5B-8B) have low photoluminescent lifetimes and quantum yields due to quenching that is proposed to involve the 3LLCT excited state and charge transfer from the [O2-bpy]2- ligand to the N,N spectator ligand. The protonated OH bearing 4,4'-dhbp Ru complexes (5A-8A) have long luminescence lifetimes which increase with increasing π expansion on the N,N spectator ligand. The Bphen complex, 8A, has the longest lifetime of the series at 3.45 μs and a photoluminescence quantum yield of 18.7%. This Ru complex also exhibits the best photocytotoxicity of the series. A long luminescence lifetime is correlated with greater singlet oxygen quantum yields because the triplet excited state is presumably long-lived enough to interact with 3O2 to yield 1O2.

Theoretical Investigation of Ru(II) Complexes with Long Lifetime and a Large Two-Photon Absorption Cross-Section in Photodynamic Therapy.

Two-photon photodynamic therapy (TP-PDT), as a new method for cancer, has shown unique advantages in tumors. A low two-photon absorption cross-section (δ) in the biologic spectral window and a short triplet state lifetime are the important issues faced by the current photosensitizers (PSs) in TP-PDT. In this paper, the photophysical properties of a series of Ru(II) complexes were studied by density functional theory and time-dependent density functional theory methods. The electronic structure, one- and two-photon absorption properties, type I/II mechanisms, triplet state lifetime, and solvation free energy were calculated. The results showed that the substitution of methoxyls by pyrene groups greatly improved the lifetime of the complex. Furthermore, the addition of acetylenyl groups subtly enhanced δ. Overall, complex 3b possess a large δ(1376 GM), a long lifetime (136 μs), and better solvation free energy. It is hoped that it can provide valuable theoretical guidance for the design and synthesis of efficient two-photon PSs in the experiment.

An Innovative Structural Rearrangement in Imine Palladacycle Metaloligand Chemistry: From Single-Nuclear to Double-Nuclear Pseudo-Pentacoordinated Complexes

Treatment of the double nuclear complex 1a, di-μ-cloro-bis[N-(4-formylbenzylidene)cyclohexylaminato-C6, N]dipalladium, with Ph2PCH2CH2)2PPh (triphos) and NH4PF6 gave the single nuclear species 2a, 1-N-(cyclohexylamine)-4-N-(formyl)palladium(triphos)(hexafluorophasphate). Reaction of 2a with Ph2PCH2CH2NH2 in refluxing chloroform via a condensation reaction of the amine and formyl groups to produce the C=N double bond, gave 3a, 1-N-(cyclohexylamine)-4- N-(diphenylphosphinoethylamine)palladium(triphos)(hexafluorophasphate); a potentially bidentate [N,P] metaloligand. However, attempts to coordinate a second metal by treatment of 3a with [PdCl2(PhCN)2] were to no avail. Notwithstanding, complexes 2a and 3a left to stand in solution spontaneously self-transformed to give in either case the double nuclear complex 10, 1,4-N,N-terephthalylidene(cyclohexilamine)-3,6-[bispalladium(triphos)]di(hexafluorophosphate), after undergoing further metalation of the phenyl ring, then bearing two mutually trans [Pd(Ph2PCH2CH2)2PPh)-P,P,P] moieties: an unprecedented and serendipitous result indeed. On the other hand, reaction of the double nuclear complex 1b, di-μ-cloro-bis[N-(3-formylbenzylidene)cyclohexylaminato-C6, N]dipalladium, with Ph2PCH2CH2)2PPh (triphos) and NH4PF6 gave the single nuclear species 2b, 1-N-(cyclohexylamine)-4-N-(formyl)palladium(triphos)(hexafluorophasphate), Treatment of 2b with H2O/glacial MeCOOH gave cleavage of the C=N double bond and of the Pd···N interaction, yielding 5b, isophthalaldehyde-6-palladium(triphos)hexafluorophosphate, which then reacted with Ph2P(CH2)3NH2 to yield complex 6b, N,N-(isophthalylidene(diphenylphosphinopropylamine)-6-(palladiumtriphos)di(hexafluorophosphate), with two pairs of non-coordinated nitrogen and phosphorus donor atoms. Treatment of 6b with [PdCl2(PhCN)2], [PtCl2(PhCN)2], or [PtMe2(COD)] gave the new double nuclear complexes 7b, 8b and 9b, palladiumdichloro-, platinumdichloro- and platinumdimethyl[N,N-(isophthalylidene(diphenylphosphinopropylamine)-6-(palladiumtriphos)(hexafluorophosphate)-P,P], respectively, showing the behavior of 6b as a palladated bidentate [P,P] metaloligand. The complexes were fully characterized by microanalysis, IR, 1H, and 31P NMR spectroscopies, as appropriate. The X-ray single-crystal analyses for compounds 10 and 5b have been previously described as the perchlorate salts by JM Vila et al.

Role of ligand disposition and oxime…oximato hydrogen bonding upon redox non-innocent character of rhodium(III) phenylazooximates

The diaryl-azo-oxime ligands HL, 1 undergoes oxidative coordination reaction with Wilkinson’s catalyst to form two isomeric complexes of type cis-[RhIIIL2Cl(PPh3)], 2a (Cl and PPh3 are cis) and trans-[RhIIIL2Cl(PPh3)], 2b where they are trans with respect to each other. Unlike the case of 2a, the complex 2b upon treatment with sodium borohydride, can be transformed to trans-[RhIII(HL●)(L–)Cl(PPh3)], 3 and the reaction appears to progress via PCET. The disposition of ligand frameworks as well as the formation of oxime…oximato hydrogen bond appears to have a significant function for phenylazooxime to exhibit redox non-innocent behaviour in presence of rhodium(III). The compounds were characterized by electrochemical analysis, different spectral methods, single crystal XRD and optoelectronic properties, particularly the nature of transitions in the chelates were scrutinized by TD-DFT.

Tin(II) and Tin(IV) Complexes Incorporating the Oxygen Tripodal Ligands [(η5-C5R5)Co{P(OEt)2O}3]−, (R = H, Me; Et = -C2H5) as Potent Inflammatory Mediator Inhibitors: Cytotoxic Properties and Biological Activities against the Platelet-Activating Factor (PAF) and Thrombin

Metal complexes displaying antiplatelet properties is a promising research area. In our methodology, Platelet-Activating Factor (PAF), the most potent lipid pro-inflammatory mediator, serves as a biological probe. The antiplatelet activity is exerted by the inhibition of the PAF-induced aggregation in washed rabbit platelets (WRPs) and in rabbit plasma rich in platelets (rPRPs). Herein, the synthesis and biological investigation of a series of organometallic tin(II) and tin(IV) complexes, featuring the oxygen tripodal Kläui ligands [(η5-C5R5)Co{P(OEt)2O}3]-, {R = H, (LOEt-); Me (L*OEt-)}, are reported. Reaction of NaLOEt (1a) and NaL*OEt (1b) with SnCl2, yielded the rare four-coordinate LOEtSnCl (2a) and L*OEtSnCl (2b) complexes. Accordingly, LOEtSnPh3 (3a) and L*OEtSnPh3 (3b) were prepared, starting from Ph3SnCl. Characterization includes spectroscopy and X-ray diffraction studies for 2a, 2b and 3b. The antiplatelet activity of the lead complexes 2b and 3a (IC50 = 0.5 μΜ) is superior compared to that of 1a and 1b, while both complexes display a pronounced inhibitory activity against thrombin (IC50 = 1.8 μM and 0.6 μM). The in vitro cytotoxic activities of 3a and 2b on human Jurkat T lymphoblastic tumor cell line is higher than that of cisplatin.

Evaluation of Ruthenium(II) N-Heterocyclic Carbene Complexes as Enzymatic Inhibitory Agents with Antioxidant, Antimicrobial, Antiparasitical and Antiproliferative Activity.

A series of [RuCl2(p-cymene)(NHC)] complexes were obtained by reacting [RuCl2(p-cymene)]2 with in situ generated Ag-N-heterocyclic carbene (NHC) complexes. The structure of the obtained complexes was determined by the appropriate spectroscopy and elemental analysis. In addition, we evaluated the biological activities of these compounds as antienzymatic, antioxidant, antibacterial, anticancer, and antiparasitic agents. The results revealed that complexes 3b and 3d were the most potent inhibitors against AchE with IC50 values of 2.52 and 5.06 μM mL-1. Additionally, 3d proved very good antimicrobial activity against all examined microorganisms with IZ (inhibition zone) over 25 mm and MIC (minimum inhibitory concentration) < 4 µM. Additionally, the ligand 2a and its corresponding ruthenium (II) complex 3a had good cytotoxic activity against both cancer cells HCT-116 and HepG-2, with IC50 values of (7.76 and 11.76) and (4.12 and 9.21) μM mL-1, respectively. Evaluation of the antiparasitic activity of these complexes against Leishmania major promastigotes and Toxoplasma gondii showed that ruthenium complexes were more potent than the free ligand, with an IC50 values less than 1.5 μM mL-1. However, 3d was found the best one with SI (selectivity index) values greater than 5 so it seems to be the best candidate for antileishmanial drug discovery program, and much future research are recommended for mode of action and in vivo evaluation. In general, Ru-NHC complexes are the most effective against L. major promastigotes.

A Pyridyl-1,2-azaborine Ligand for Phosphorescent Neutral Iridium(III) Complexes

A novel 1,2-azaborine (i.e., 4-methyl-2-(pyridin-2-yl)-2,1-borazaronaphthalene, 1a) has been synthesized and used for the first time as a B-N alternative to common cyclometalating ligands to obtain neutral phosphorescent iridium(III) complexes (i.e., 2a, 3, and 4) of general formula [Ir(C∧N)2(N∧NB)], where C∧N indicates three different cyclometalating ligands (Hppy = 2-phenylpyridine; Hdfppy = 2-(2,4-difluoro-phenyl)pyridine; Hpqu = 2-methyl-3-phenylquinoxaline). Moreover, the azaborine-based complex 2a was compared to the isoelectronic C═C iridium(III) complex 2b, obtained using the corresponding 2-(naphthalen-2-yl)pyridine ligand 1b. Due to the dual cyclometalation mode of such C═C ligand, the isomeric complex 2c was also obtained. All new compounds have been fully characterized by NMR spectroscopy and high-resolution mass spectrometry (MS), and the X-ray structure of 2a was determined. The electronic properties of both ligands and complexes were investigated by electrochemical, density functional theory (DFT), and photophysical methods showing that, compared to the naphthalene analogues, the azaborine ligand induces a larger band gap in the corresponding complexes, resulting in increased redox gap (basically because of the highest occupied molecular orbital (HOMO) stabilization) and blue-shifted emission bands (e.g., λmax = 523 vs 577 nm for 2a vs 2b, in acetonitrile solution at 298 K). On the other hand, the 3LC nature of the emitting state is the same in all complexes and remains centered on the pyridyl-borazaronaphthalene or its C═C pyridyl-naphthalene analogue. As a consequence, the quantum yields of such azaborine-based complexes are comparable to those of the more classical C═C counterparts (e.g., photoluminescence quantum yield (PLQY) = 16 vs 22% for 2a vs 2b, in acetonitrile solution at 298 K) but with enhanced excited-state energy. This proves that such type of azaborine ligands can be effectively used for the development of novel classes of photoactive transition-metal complexes for light-emitting devices or photocatalytic applications.

Binuclear Cu(II), Ni(II) and Zn(II) complexes of hydrazone Schiff bases: Synthesis, spectroscopy, DFT calculations, and SOD mimetic activity

Two new salicylaldimine-based N-heterocyclic hydrazone ligands, N'-[(2-hydroxyphenyl) methylene]-2-(2-phenyl-1H-benzimidazol-1-yl)acetohydrazone (H2L1) and 2-[2-(3-chlorobenzyl)-1H-benzimidazol-1-yl]-N'-[(2-(hydroxyimino)-1-ethylpropylidene]aceto hydrazone (H2L2) and their homo-binuclear nickel(II), copper(II) and zinc(II) complexes have been synthesized and their structures were identified by using spectroscopic techniques and elemental analysis. The two ligands in both the solid state and solution state show tautomerism, but their complexes don't show tautomerism due to the deprotonation and metal ion(s) binding the ligand in the enol-imine-enol form. The stoichiometries of the complexes were also confirmed by thermal analysis with formation of the corresponding metal oxides. TD-DFT calculations have also been performed to correlate geometrical parameters with the spectral properties of compounds and to assign vibrations and electronic transitions. Evaluations of the mimetic catalytic activities of the complexes for the superoxide dismutase (SOD) enzyme were also performed through in vitro tests. All of the complexes studied exhibit activity and the Cu(II) complex (3b) shows the highest activity with the lowest IC50 value (2.50 ± 0.60 µM).

Synthesis and conjugation properties of alkynyl functionalized salicylidene Ni(II) and Zn(II) phosphine complexes and their use as a precursor for preparation of NiO and ZnO nanoparticles

The complexes of type [Ni(L1/L2 )(PPh3)2/dppe]NO3 (1a-4a) and [Zn(L1/L2 )(PPh3)2/(dppe)]NO3 (1b-4b) [where L1 = 2-((E)-(4-(2-(trimethylsilyl)ethynyl)phenylimino)methyl)-4-(2-(4-bromophenyl)ethynyl) phenol; L2 = 2-((E)-(4-(2-(trimethylsilyl)ethynyl)phenylimino)methyl)-4-(2-(4-methoxyphenyl)ethynyl) phenol; PPh3 = triphenylphosphine; and dppe = 1, 2-bis(diphenylphosphino)ethane] have been synthesized and characterized by elemental analyses, IR, UV–Vis, 1H NMR, and 31P NMR spectral studies. The ancillary phosphine ligands significantly perturb the metal to ligand charge transfer (MLCT) state of Ni(II) and Zn(II) complexes and associated with their electron donating character. The room temperature luminescence is observed for all complexes which corresponds to π→π* ILCT transition with some MLCT character. The second harmonic generation (SHG) efficiency of the complexes was determined by Kurtz-powder technique indicating that all complexes displayed the SHG property. Metal oxide nanoparticles were obtained by calcinations of representative complexes 1a and 4b at 600 °C and are characterized by FTIR, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction techniques.

C-N linked donor type porphyrin derivatives: unrevealed hole-transporting materials for efficient hybrid perovskite solar cells.

A new series of Zn(II) and Cu(II)-based porphyrin complexes 5a and 5b doubly functionalised with carbazole units were developed to be used as hole-transporting materials (HTMs) in perovskite solar cells (PSCs). These complexes were obtained via a nucleophilic substitution reaction mediated by PhI(OAc)2/NaAuCl4·2H2O, or using C-N transition metal-assisted coupling. The hole extraction capability of 5a and 5b was assessed using cyclic voltammetry; this study confirmed the better alignment of the Zn(II) complex 5a with the perovskite valence band level, compared to the Cu(II) complex 5b. The optimised geometry and molecular orbitals of both complexes also corroborate the higher potential of 5a as a HTM. Photoluminescence characterisation showed that the presence of 5a and 5b as HTMs on the perovskite surface resulted in the quenching of the emission, matching the hole transfer phenomenon. The photovoltaic performance was evaluated and compared with those of reference cells made with the standard HTM spiro-OMeTAD. The optimised 5-based devices showed improvements in all photovoltaic characteristics; their open circuit voltage (Voc) reached close to 1 V and short-circuit current density (Jsc) values were 13.79 and 9.14 mA cm-2 for 5a and 5b, respectively, disclosing the effect of the metallic centre. A maximum power conversion efficiency (PCE) of 10.01% was attained for 5a, which is 65% of the PCE generated by using the spiro-OMeTAD reference. This study demonstrates that C-N linked donor-type porphyrin derivatives are promising novel HTMs for developing efficient and reproducible PSCs.