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The organoplatinum complexes cis -[PtAr 2 (SMe 2 ) 2 ] (Ar = p– MeC 6 H 4 and p– MeOC 6 H 4 ) and cis,cis -[Me 2 Pt(μ-SMe 2 ) 2 PtMe 2 ] react very easily - in acetone at room temperature - with 1 or 2 equiv 1,1′–bis(diphenylphosphino)acetylene (= dppac), to give the diplatinum(II) complexes [Pt 2 R 4 (μ–dppac) 2 ], ( 1 , R = Me; 2 , R = p– MeC 6 H 4 ; 3 , R = p– MeOC 6 H 4 ) in which two square-planar R 2 Pt units are held together by two bridging dppac ligands. All the complexes were characterized using multinuclear ( 1 H, 31 P and 195 Pt) NMR spectroscopy and single crystal X-ray structure determination. Investigation of electronic structures and related DFT and TD-DFT calculations supported a mixed 1 IL (intraligand charge transfer)/ 1 MLCT (metal-to-ligand charge transfer) for R = Me and L'LCT (ligand-to-ligand charge transfer) for R = p– MeC 6 H 4 and p– MeOC 6 H 4 . [ABSTRACT FROM AUTHOR]

Abstract: Binuclear cycloplatinated(II) complexes with general formula of [Pt2Me2(CˆN)2(μ-dppac)], (1, CˆN = deprotonated 2-phenylpyridine (ppy); 2, CˆN = deprotonated benzo{h}quinoline (bhq)) in which dppac = 1,1′-bis(diphenylphosphino)acetylene, are synthesized by the reaction of [PtMe(SMe2)(CˆN)] with 0.5 equiv of dppac at room temperature. The complexes are fully characterized using multinuclear (1H, 31P and 195Pt) NMR spectroscopy and complex 2 is further identified by single crystal X-ray structure determination. Kinetics of the reaction of complexes 1 and 2 with MeI are investigated in CHCl3 and based on the UV–vis and 31P NMR data, a mechanism involving a double MeI oxidative addition is suggested. The classical SN2 mechanism is proposed for both steps and the involved intermediates are suggested. Although MeI in each step was trans oxidatively added to one of the platinum(II) centers, further trans to cis isomerizations of methyl and iodide ligands were also identified. The rates are almost four times slower in the second step as compared to the first step due to the electronic effects transmitted through the dppac ligand. Reaction rates concerning complex 2, having bhq ligand, are almost 1.3 times slower than those involving the related ppy complex 1. This is attributed to the stronger donor ability of the ppy ligand, as compared to that bhq ligand and is in agreement with the values of 1 J PtP observed in the 31P NMR spectra of the complexes 1 and 2. The structure of the Pt(IV)–Pt(IV) dimeric complex [Pt2I2Me4(ppy)2(μ-dppac)], 3, produced by oxidative addition of complex 1 to MeI, is also determined using X-ray diffraction which is the first X-ray structural determination of a diplatinum complex containing two Pt(IV) centers bridged by one dppac ligand. [Copyright &y& Elsevier]

The effects of several imidazolium-based ionic liquids on the rate of the oxidative addition reactions of organoplatinum(ii) complexes [Pt(p-MeC6H4)2(NN)], in which NN is either 1,10-phenanthroline (phen), 1a, or 4,4′-di-tert-butyl-2,2′-bipyridine (tBu2bpy), 1b, with MeI to give the organoplatinum(iv) products [Pt(p-MeC6H4)2MeI(NN)] were investigated as a function of the ionic liquid (as solvent) using UV-vis spectroscopy techniques. The obtained rate constants and activation parameters showed a dependence on the nature of the anionic component of the ionic liquid as related to the polarity/polarizability parameter, π*, of the ionic liquids. [ABSTRACT FROM AUTHOR]

Here we report on a scanning tunnelling microscopy (STM) investigation on the self-assembly of C 3 - and C 2 -symmetric molecules at the solution/graphite interface. 1,3,5-tris(( E )-2-(pyridin-4-yl)vinyl)benzene and 1,1,2,2-tetrakis(4-(pyridin-4-yl)phenyl)ethane are used as model systems. These molecules displayed a concentration dependent self-assembly behaviour on graphite, resulting in highly ordered supramolecular structures, which are stabilized jointly by van der Waals substrate-adsorbate interactions and in-plane intermolecular H-bonding. Denser packing is obtained when applying a relatively high concentration solution to the basal plane of the surface whereas a less dense porous network is observed upon lowering the concentration. We show that the molecular conformation does not influence the stability of the self-assembly and a twisted molecule can pack into dense and porous architectures under the concentration effect. [ABSTRACT FROM AUTHOR]

Reaction of the known cycloplatinated (II) complexes [PtAr(C^N)(SMe 2 )], in which Ar= p– MeC 6 H 4 or p– MeOC 6 H 4 and C^N= 2-phenylpyridinate (ppy) or benzo[h]quinolinate (bhq), with 0.5 equivalent of the bidentate phosphine ligand 1,1′–bis(diphenylphosphino)acetylene, dppac, in acetone at room temperature gave the symmetrical binuclear cycloplatinated(II) complexes [Pt 2 Ar 2 (C^N) 2 (μ–dppac)], 1–4 , in which dppac acts as a bridging bidentate ligand. All the complexes were fully characterized using multinuclear ( 1 H, 31 P and 195 Pt) NMR spectroscopy and the complex [Pt 2 ( p– MeC 6 H 4 ) 2 (ppy) 2 (μ–dppac)], 1 , was further identified by single crystal X-ray structure determination. Additional information about the geometries and electronic spectra of these cycloplatinated (II) complexes are discussed. Effects of aryl and C^N ligands on the luminescent properties of the complexes were also investigated that are complying well with the related DFT/TD-DFT calculations. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) continue to attract increasing interest with respect to their applications as luminescent materials. The ordered structure of the metal-organic complex facilitates the selective integration of PAHs that can be tuned to function cooperatively. Here, a unique highly twisted anthracene-based organoplatinum metallacycle was prepared via coordination-driven selfassembly. Single-crystal X-ray diffraction analysis revealed that the metallacycle was twisted through the cooperation of strong π···π stacking interactions and steric hindrance between two anthracenebased ligands. Notably, the intramolecular twist and aggregation behavior introduced restrictions to the conformational change of anthracenes, which resulted in increased emission intensity of the metallacycle in solution. The emission behaviors and suprastructures based on the highly twisted metallacycle can be modulated by the introduction of different solvents. This study demonstrates that this metallacycle with highly twisted structure is a promising candidate for sensing and bioimaging applications. [ABSTRACT FROM AUTHOR]

Despite the widespread clinical application of chemotherapeutic anticancer drugs, their adverse side effects and inefficient performances remain ongoing issues. A drug delivery system (DDS) designed for a specific cancer may therefore overcome the drawbacks of single chemotherapeutic drugs and provide precise and synergistical cancer treatment by introducing exclusive stimulus responsiveness and combined chemotherapy properties. Herein, we report the design and synthesis of a supramolecular drug delivery assembly 1 constructed by orthogonal self-assembly technique in aqueous media specifically for application in liver cancer therapy. Complex 1 incorporates the β-cyclodextrin host moleculefunctionalized organoplatinum(II) metallacycle 2 with two specific stimulus-responsive motifs to the signaling molecule nitric oxide (NO), in addition to the three-armed polyethylene glycol (PEG) functionalized ferrocene 3 with redox responsiveness. With this molecular design, the particularly low critical aggregation concentration (CAC) of assembly 1 allowed encapsulation of the commercial anticancer drug doxorubicin (DOX). Controlled drug release was also achieved by morphological transfer via a sensitive response to the endogenous redox and NO stimuli, which are specifically related to the microenvironment of liver tumor cells. Upon combination of these properties with the anticancer ability from the platinum acceptor, in vitro studies demonstrated that DOX-loaded 1 is able to codeliver anticancer drugs and exhibit therapeutic effectiveness to liver tumor sites via a synergistic effect, thereby revealing a potential DDS platform for precise liver cancer therapeutics. [ABSTRACT FROM AUTHOR]

Herein, we report the preparation of a multifunctional metallacage-core supramolecular gel by orthogonal metal coordination and host-guest interactions. A tetragonal prismatic cage with four appended 21-crown-7 (21C7) moieties in its pillar parts was first prepared via the metal-coordination-driven self-assembly of cis-Pt(PEt3)2-(OTf)2, tetraphenylethene (TPE)-based sodium benzoate ligands and linear dipyridyl ligands. Further addition of a bisammonium linker to the cage delivered a supramolecular polymer network via the host-guest interactions between the 21C7 moieties and ammonium salts, which formed a supramolecular gel at relatively higher concentrations. Due to the incorporation of a TPE derivative as the fluorophore, the gel shows emission properties. Multiple stimuli responsiveness and good self-healing properties were also observed because of the dynamic metal coordination and host-guest interactions used to stabilize the whole network structure. Moreover, the storage and loss moduli of the gel are 10-fold those of the gel without the metallacage cores, indicating that the rigid metallacage plays a significant role in enhancing the stiffness of the gel. The studies described herein not only enrich the functionalization of fluorescent metallacages via elegant ligand design but also provide a way to prepare stimuli-responsive and self-healing supramolecular gels as robust and smart materials. [ABSTRACT FROM AUTHOR]

Two novel discrete organoplatinum(II) metallacycles are prepared by means of coordination-driven self-assembly of a 90° organoplatinum(II) acceptor, cis-(PEt3)2Pt(OTf)2, with two donors, a pyridyl donor, 9,10-di(4-pyridylvinyl)anthracene, and one of two dicarboxylate ligands. Both metallacycles display aggregation-induced emission as well as solvatochromism. More interestingly, both metallacycles exhibit near-infrared fluorescent emission in the solid state and can be used to detect ammonia gas. [ABSTRACT FROM AUTHOR]

Some new cobalt(III) complexes described as [Co(Chel)(PBu3)]ClO4 × H2O where (Chel) is the deprotonated form of a series of symmetric and unsymmetrical Schiff base ligands containing 3,4-diaminobenzophenone (3,4-DABP) and substituted salicylaldehyde moieties and [Co(Chel)(PMePh2)]ClO4 × H2O where (Chel) is [N'-(5-BrSalDABP)] were synthesized and characterized by ¹H NMR, IR, UV-Vis spectroscopy, and elemental analysis. The formation constants and the thermodynamic parameters were determined spectrophotometrically for 1: 1 adduct formation of the new complexes as acceptor with some aliphatic amines such as benzylamine, n-butylamine, sec-butylamine and tertbutylamine as donors in DMSO solvent in constant ionic strength (I = 0.1 M NaClO4). The formation constants change according to the following trend due to the steric and the electronic factors of the cobalt(III) complexes: N'-5-OMe > N'-5-H > N'-5-Br > N'-5-Cl; N,N'-3-OMe > N,N'-4-Ome.. The trend of the formation constants of cobalt(III) Schiff base complexes toward a given donor according to the axial ligand is as follow: PBu3 > PMePh2. Also, the following binding trend of the donors toward a given cobalt(III) Schiff base complex is obtained: benzylamine > n-butylamine > sec-butylamine > tert-butylamine. [ABSTRACT FROM AUTHOR]