Synthesis, Luminescence, and Electrochemistry of Tris-Chelate Platinum(IV) Complexes with Cyclometalated N-Heterocyclic Carbene Ligands and Aromatic Diimines.

Dicationic, -symmetrical, tris-chelate Pt(IV) complexes of general formula [Pt(trz)(N∧N)](OTf), bearing two cyclometalated 4-butyl-3-methyl-1-phenyl-1-1,2,3-triazol-5-ylidene (trz) ligands and one aromatic diimine [N∧N = 2,2'-bipyridine (bpy, ), 4,4'-di--butyl-2,2'-bipyridine (dbbpy, ), 4,4'-dimethoxi-2,2'-bipyridine (dMeO-bpy, ), 1,10-phenanthroline (phen, ), 4,7-diphenyl-1,10-phenanthroline (bphen, ), dipyrido[3,2-:2',3'-]phenazine (dppz, ), or 2,3-diphenylpyrazino[2,3-][1,10]phenanthroline (dpprzphen, )] are obtained through chloride abstraction from [PtCl(trz)] () using AgOTf in the presence of the corresponding diimine. Complexes show long-lived phosphorescence from LC excited states involving the diimine ligand, with quantum yields that reach 0.18 in solution and 0.

A Novel Substituted Benzo[]quinoxaline-Based Cyclometalated Ru(II) Complex as a Biocompatible Membrane-Targeted PDT Colon Cancer Stem Cell Agent.

Herein, we describe and investigate biological activity of three octahedral ruthenium(II) complexes of the type [Ru(CN)(phen)], -, containing a π-expansive cyclometalating substituted benzo[]quinoxaline ligand (CN ligand) (phen = 1,10-phenanthroline). Compounds - in cervical, melanoma, and colon human cancer cells exhibit high phototoxicity after irradiation with light (particularly blue), with the phototoxicity index reaching 100 for the complex in most sensitive HCT116 cells. accumulates in the cellular membranes.

Cycloadditions of 4-Alkenyl-2-aminothiazoles with Nitroalkenes in the Formal Synthesis of Pramipexole: An Experimental and Computational Study.

4-Alkenyl-2-dialkylaminothiazoles act as in-out dienes in [4 + 2] cycloaddition reactions with nitroalkenes, furnishing 2-amino-6-nitro-4,5,6,7-tetrahydrobenzothiazoles in moderate to good yields, accompanied by a subsequent 1,3- migration. These transformations proceed with exquisite site-, regio-, and diastereoselectivity. This strategy is further enriched by revealing a novel route for pramipexole synthesis.

Rational Design of 7-Azaindole-Based Robust Microporous Hydrogen-Bonded Organic Framework for Gas Sorption.

7-Azaindole has been integrated as building block with complementary N-H⋅⋅⋅N hydrogen bonding sites for the synthesis of a tetrahedral molecular tecton, namely tetra(α-carbolin-6-yl)methane, TACM. The self-assembly of this molecule results in a 3D hydrogen-bonded organic framework (HOF). This supramolecular structure constitutes a crystalline microporous material with an extraordinary thermal and chemical robustness.

Pd-Catalyzed Ring-Opening Polymerization of Cyclobutanols through C(sp)-C(sp) Bond Cleavage.

A new approach to ring-opening polymerization (ROP) based on C(sp)-C(sp) bond cleavage is reported. This process is based on the ability of Pd to promote both the β-carbon elimination of a bifunctional cyclobutanol precursor and the C-C coupling process with the resulting Pd-alkyl intermediate. Consequently, novel polyketone materials are obtained.

Photoactivatable Ruthenium Complexes Containing Minimal Straining Benzothiazolyl-1,2,3-triazole Chelators for Cancer Treatment.

Ruthenium(II) complexes containing diimine ligands have contributed to the development of agents for photoactivated chemotherapy. Several approaches have been used to obtain photolabile Ru(II) complexes. The two most explored have been the use of monodentate ligands and the incorporation of steric effects between the bidentate ligands and the Ru(II).

Novel 2-(5-Arylthiophen-2-yl)-benzoazole Cyclometalated Iridium(III) dppz Complexes Exhibit Selective Phototoxicity in Cancer Cells by Lysosomal Damage and Oncosis.

A second-generation series of biscyclometalated 2-(5-aryl-thienyl)-benzimidazole and -benzothiazole Ir(III) dppz complexes [Ir(C^N)(dppz)], -, were rationally designed and synthesized, where the aryl group attached to the thienyl ring was -CFCH or -MeNCH. These new Ir(III) complexes were assessed as photosensitizers to explore the structure-activity correlations for their potential use in biocompatible anticancer photodynamic therapy. When irradiated with blue light, the complexes exhibited high selective potency across several cancer cell lines predisposed to photodynamic therapy; the benzothiazole derivatives ( and ) were the best performers, being also activatable with green or red light.

Luminescent Platinum(II) Complexes with Terdentate N∧C∧C Ligands.

The synthesis, structure, and luminescence of Pt(II) complexes of the type [Pt(N∧C∧C)(L)] are reported, where N∧C∧C is a terdentate ligand resulting from the cycloplatination of 2-(3,5-diphenoxyphenyl)pyridine or 2-(4,4″-dimethyl-[1,1':3',1″-terphenyl]-5'-yl)pyridine, and L represents a monodentate ancillary ligand, which can be γ-picoline, 4-pyridinecarboxaldehyde, PPh, butyl or 2,6-dimethylphenyl isocyanide, CO, or the N-heterocyclic carbenes 1-butyl-3-methylimidazol-2-ylidene or 4-butyl-3-methyl-1-phenyl-1-1,2,3-triazol-5-ylidene. Derivatives bearing CO, isocyanides, or carbenes showed the highest stabilities in solution, whereas the pyridine and PPh derivatives establish ligand-exchange equilibria in acetonitrile. Different supramolecular structures are observed in the solid state, which largely depend on the nature of the ancillary ligand.

Photoinduced Reductive C-C and C-Heteroatom Couplings from Bis-cyclometalated Pt(IV) Alkynyl Complexes.

Unsymmetrical dicarboxylato complexes [Pt(tpy)(OCR)] [tpy = cyclometalated 2-(-tolyl)pyridine, R = Me, CF] react with the terminal alkynes 4-methoxyphenylacetylene, phenylacetylene, 4-(trifluoromethyl)phenylacetylene or 3,5-difluorophenylacetylene in the presence of a base to produce complexes -[Pt(tpy)(OCR)(CCAr)], in which the metalated carbon atoms are in a meridional arrangement. Irradiation of the trifluoroacetato derivatives with a 365 nm LED source leads to isomerization to the facial complexes, which can be converted to chlorido derivatives upon reaction with NHCl. In contrast, irradiation of the acetato derivatives leads to four different processes, namely, reduction to -[Pt(tpy)], annulations involving one of the tpy ligands and the C and C atoms of the alkynyl to give benzoquinolizinium derivatives, isomerization to the facial geometry, or C-O couplings between the acetato ligand and one tpy.

Novel valproate half-sandwich rhodium and iridium conjugates to fight against multidrug-resistant Gram-positive bacteria.

New valproate Ir(III) and Rh(III) half-sandwich conjugates containing a C,N-phenylbenzimidazole chelated ligand have been synthesized and characterized. The valproic acid conjugation to organometallic fragments seems to switch on the antibacterial activity of the complexes towards and Gram-positive bacteria.

Photochemically Induced Cyclometalations at Simple Platinum(II) Precursors.

Photochemical cycloplatinations of 2-arylpyridines and related C∧N ligands, as well as terdentate heteroaromatic N∧N∧C, N∧C∧N, and N∧C∧C compounds, are demonstrated using (BuN)[PtCl] or [PtCl(NCPh)] as precursors at room temperature. Mono- or bis-cyclometalated Pt(II) complexes with C∧N ligands are obtained depending on excitation wavelength and precursor. Monitoring experiments show that photoexcitation enables both the N-coordination and the subsequent C-H metalation.

Cyclometalated Benzimidazole Osmium(II) Complexes with Antiproliferative Activity in Cancer Cells Disrupt Calcium Homeostasis.

We present the synthesis and characterization of six new heteroleptic osmium(II) complexes of the type [Os(C^N)(N^N)]OTf (N^N = 2,2'-bipyridine and dipyrido[3,2-:2',3'-]quinoxaline; C^N = deprotonated methyl 1-butyl-2aryl-benzimidazolecarboxylate) with varying substituents in the R3 position of the phenyl ring of the cyclometalating C^N ligand. The new compounds are highly kinetically inert and absorb a full-wavelength range of visible light. An investigation of the antiproliferative activity of the new compounds has been performed using a panel of human cancer and noncancerous 2D cell monolayer cultures under dark conditions and green light irradiation.

Reductive Elimination Reactions in Gold(III) Complexes Leading to C(sp)-X (X = C, N, P, O, Halogen) Bond Formation: Inner-Sphere vs S2 Pathways.

The reactions leading to the formation of C-heteroatom bonds in the coordination sphere of Au(III) complexes are uncommon, and their mechanisms are not well known. This work reports on the synthesis and reductive elimination reactions of a series of Au(III) methyl complexes containing different Au-heteroatom bonds. Complexes [Au(CF)(Me)(X)(PR)] (R = Ph, X = OTf, OClO, ONO, OC(O)CF, F, Cl, Br; R = Cy, X = Me, OTf, Br) were obtained by the reaction of -[Au(CF)(Me)(PR)] (R = Ph, Cy) with HX.

Phosphorescent Tris-cyclometalated Pt(IV) Complexes with Mesoionic -Heterocyclic Carbene and 2-Arylpyridine Ligands.

The synthesis, structure, photophysical properties, and electrochemistry of the first series of Pt(IV) tris-chelates bearing cyclometalated aryl-NHC ligands are reported. The complexes have the general formula [Pt(trz)(C∧N)], combining two units of the cyclometalated, mesoionic aryl-NHC ligand 4-butyl-3-methyl-1-phenyl-1-1,2,3-triazol-5-ylidene (trz) with a cyclometalated 2-arylpyridine [C∧N = 2-(2,4-difluorophenyl)pyridine (dfppy), 2-phenylpyridine (ppy), 2-(-tolyl)pyridine (tpy), 2-(2-thienyl)pyridine (thpy), 2-(9,9-dimethylfluoren-2-yl)pyridine (flpy)], and presenting a arrangement or metalated aryls. They exhibit a significant photostability under UV irradiation and long-lived phosphorescence in the blue to yellow color range, arising from LC excited states involving the C∧N ligands, with quantum yields of up to 0.

Synthesis of Benzofused - and -Heterocycles through Cascade Carbopalladation/Cross-Alkylation of Alkynes Involving the C-C Cleavage of Cyclobutanols.

We report a Pd-catalyzed route to heterocycles bearing a tetrasubstituted alkene fragment. Our approach merges the intramolecular carbopalladation of tethered alkynes with an alkylation step produced by the C-C cleavage of cyclobutanol derivatives. An alkenyl-Pd(II) intermediate has been isolated and characterized by X-ray diffraction studies.

Phosphorescent biaryl platinum(IV) complexes obtained through double metalation of dibenzoiodolium ions.

The first series of neutral, tris-chelate, phosphorecent Pt(IV) complexes is reported, which combine two cyclometalated 2-arylpyridine ligands and a dimetalated biaryl. The introduction of biaryl ligands is achieved under mild conditions through the oxidative addition of dibenzoiodolium ions to Pt(II) precursors to give Pt(IV) intermediates with a singly metalated 2-(2-iodoaryl)aryl ligand, followed by the reductive metalation of the C-I bond. The modulation of emission characteristics derivatization of both types of ligands is demonstrated.

Sequential Insertion of Alkynes, Alkenes, and CO into the Pd-C Bond of -Palladated Primary Phenethylamines: from η-Allyl Complexes and Enlarged Palladacycles to Functionalized Arylalkylamines.

The eight-membered metallacycles arising from the insertion of 1 equiv of alkyne into the Pd-C bond of -metalated homoveratrylamine and phentermine can further react with alkenes to give two different types of mononuclear complexes depending on the nature of the olefin. When terminal alkenes (styrene and ethyl acrylate) are used, a mixture of the / η-allyl Pd(II) complexes are isolated, which evolve slowly to the isomers by heating the mixtures appropriately. These η-allyl Pd(II) complexes do not react with CO or weak bases, but when they are treated with a strong base, such as KOBu, they afford Pd(0) and the functionalized starting phenethylamines containing a 1,3-butadienyl substituent in an position.

Luminescent halido(aryl) Pt(IV) complexes obtained oxidative addition of iodobenzene or diaryliodonium salts to bis-cyclometalated Pt(II) precursors.

The synthesis of bis-cyclometalated halido(aryl) Pt(IV) complexes [PtX(Ar)(C^N)], with C^N = cyclometalated 4-(-butyl)-2-phenylpyridine (bppy), 2-(-tolyl)pyridine (tpy), 2-(2-thienyl)pyridine (thpy), or 1-phenylisoquinoline (piq), X = I, Cl, or F, and Ar = Ph (for all C^N ligands) or -BuPh (for C^N = tpy), and the photophysical properties of the chlorido and fluorido series is reported. The oxidative addition of iodobenzene to -[Pt(C^N)] precursors is demonstrated to occur in MeCN under irradiation with visible light to give complexes [PtI(Ph)(C^N)], presumably involving radical species that also produce the activation of the solvent to give cyanomethyl complexes [PtI(CHCN)(C^N)]. The introduction of an aryl ligand can also be achieved by reacting -[Pt(C^N)] with (ArI)PF (Ar = Ph, -BuPh), which affords cationic intermediates of the type [Pt(Ar)(C^N)(NCMe)].

Dinuclear Au(I), Au(II) and Au(III) Complexes with (CF ) Chains: Insights into The Role of Aurophilic Interactions in the Au(I) Oxidation.

New dinuclear Au(I), Au(II) and Au(III) complexes containing (CF ) bridging chains were obtained. Metallomacrocycles [Au {μ-(CF ) }{μ-diphosphine}] show an uncommon figure-eight structure, the helicity inversion barrier of which is influenced by aurophilic interactions and steric constraints imposed by the diphosphine. Halogenation of LAu(CF ) AuL (L=PPh , PMe , (dppf) , (binap) ) gave [Au(II)] species, some of which display unprecedented folded structures with Au-Au bonds.

Cyclization of interlocked fumaramides into β-lactams: experimental and computational mechanistic assessment of the key intercomponent proton transfer and the stereocontrolling active pocket.

A detailed mechanistic study of the diastereoselective CsOH-promoted cyclization of interlocked fumaramides to give β-lactams is described. The mechanistic analysis comprises the experimental evaluation of the structure-reactivity relationship for a wide range of fumaramides [2]rotaxanes (Hammet-plots), KIE studies with deuterium-labelled interlocked fumaramides and computational analysis of two alternative mechanistic pathways for the cyclization process. The obtained results confirm that: (a) the rate-determining step is the deprotonation of the -benzyl group of the thread by the amidate group of the macrocycle generated by the external base, (b) the polyamide macrocycle plays an important role not only as activating element but also as the stereodifferenciating factor responsible for the observed diastereoselection and (c) the higher flexibility of the adamantyl core speeds up the cyclization process in diadamantyl-derived rotaxanes.

Visible light driven generation and alkyne insertion reactions of stable bis-cyclometalated Pt(iv) hydrides.

Hydride complexes resulting from the oxidative addition of C-H bonds are intermediates in hydrocarbon activation and functionalization reactions. The discovery of metal systems that enable their direct formation through photoexcitation with visible light could lead to advantageous synthetic methodologies. In this study, easily accessible dimers [Pt(μ-Cl)(C^N)] (C^N = cyclometalated 2-arylpyridine) are demonstrated as a very convenient source of Pt(C^N) subunits, which promote photooxidative C-H addition reactions with different 2-arylpyridines (N'^C'H) upon irradiation with blue light.

Strongly Luminescent Pt(IV) Complexes with a Mesoionic -Heterocyclic Carbene Ligand: Tuning Their Photophysical Properties.

The synthesis, electrochemistry, and photophysical properties of a series of bis-cyclometalated Pt(IV) complexes that combine the mesoionic aryl-NHC ligand 4-butyl-3-methyl-1-phenyl-1-1,2,3-triazol-5-ylidene (trz) with either 1-phenylpyrazole or 2-arylpyridine (CN) are reported. The complexes (-6-54)-[PtCl(CN)(trz)] bearing cyclometalating 2-arylpyridines present phosphorescent emissions in the blue to yellow color range, which essentially arise from LC(CN) states, and reach quantum yields of ca. 0.

Effective Encapsulation of C by Metal-Organic Frameworks with Polyamide Macrocyclic Linkers.

A flexible benzylic amide macrocycle, functionalized with two carboxylic acid groups, was employed as the organic ligand for the preparation of robust copper(II)- and zinc(II)-based metal-organic frameworks. These polymers crystallized in the C2/m space group of the monoclinic crystal system, creating non-interpenetrated channels in one direction with an extraordinary solvent-accessible volume of 46 %. Unlike metal-organic rotaxane frameworks having benzylic amide macrocycles as linkers, the absence of the thread in these novel reticular materials causes a decrease of dimensionality and an improvement of pore size and dynamic guest adaptability.

Ru(ii) photosensitizers competent for hypoxic cancers via green light activation.

A family of five heteroleptic complexes [Ru(C^N)(N^N)][PF] (HC^N = methyl 1-butyl-2-arylbenzimidazolecarboxylate; N^N = polypyridine) has been synthesized to act as biologically-compatible green light photosensitizers (PSs) with phototherapeutic indexes (PIs) up to higher than 700 under hypoxia (2% O) in HeLa cancer cells under short time of irradiation.

Copper-Linked Rotaxanes for the Building of Photoresponsive Metal Organic Frameworks with Controlled Cargo Delivery.

We have prepared a photoresponsive metal-organic framework by using an amide-based [2]rotaxane as linker and copper(II) ions as metal nodes. The interlocked linker was obtained by the hydrogen bond-directed approach employing a fumaramide thread as template of the macrocyclic component, this latter incorporating two carboxyl groups. Single crystal X-ray diffraction analysis of the metal-organic framework, prepared under solvothermal conditions, showed the formation of stacked 2D rhombohedral grids forming channels decorated with the interlocked alkenyl threads.