[2,6‐Bis(5‐methyl‐2‐pyridyl)phenyl‐κ3N,C1,N′]chloridoplatinum(II)

In the title compound, [Pt(C₁₈H₁₅N₂)Cl], the Pt^II centre adopts a distorted square‐planar coordination geometry due to the pincer‐type monoanionic N–C–N tridentate ligand. The planar complexes stack viaπ–π interactions to form two‐dimensional accumulated sheets. This packing pattern is in contrast to that in related pincer‐type N–C–N complexes, which exhibit a one‐dimensional columnar stacking.     

Mesomorphism and luminescence properties of platinum(II) complexes with tris(alkoxy)phenyl-functionalized pyridyl pyrazolate chelates

A series of new mesomorphic platinum(II) complexes 1 – 4 bearing pyridyl pyrazolate chelates are reported herein. In this approach, pyridyl azolate ligands have been strategically functionalized with tris(alkoxy)phenyl groups with various alkyl chain lengths. As a result, they are ascribed to a class of luminescent metallomesogens that possess distinctive morphological properties, such as their intermolecular packing arrangement and their associated photophysical behavior. In CH₂Cl₂, independent of the applied concentration in the range 10^?6–10^?3 M , all Pt^II complexes exhibit bright phosphorescence centered at around 520 nm, which is characteristic for monomeric Pt^II complexes. In stark contrast, the single‐crystal X‐ray structure determination of [Pt(C4pz)₂] ( 1 ) shows the formation of a dimeric aggregate with a notable Pt???Pt contact of 3.258 Å. Upon heating, all Pt^II complexes 1 – 4 melted to form columnar suprastructures, for which similar intracolumnar Pt???Pt distances of approx. 3.4–3.5 Å are observed within an exceptionally wide temperature range (>250 °C), according to the powder XRD data. Upon casting into a neat thin film at RT, the luminescence of 1 – 4 is dominated by a red emission that spans 630–660 nm, which originates from the one‐dimensional, chainlike structure with Pt–Pt interaction in the ground state. Taking complex 4 as a representative, the emission intensity and wavelength were significantly decreased and blueshifted, respectively, on heating from RT to 250 °C. Further heating to liquefy the sample alters the red emission back to the green phosphorescence of the monomer. The results highlight the pivotal role of tris(alkoxy)phenyl groups in the structural versus luminescence behavior of these Pt^II complexes.     

Photolysis and Thermolysis of Platinum(IV) 2,2′‐Bipyridine Complexes Lead to Identical Platinum(II)–DNA Adducts

Two Pt^IV and two Pt^II complexes containing a 2,2′‐bipyridine ligand were treated with a short DNA oligonucleotide under light irradiation at 37 °C or in the dark at 37 and 50 °C. Photolysis and thermolysis of the Pt^IV complexes led to spontaneous reduction of the Pt^IV to the corresponding Pt^II complexes and to binding of Pt^II 2,2′‐bipyridine complexes to N7 of guanine. When the reduction product was [Pt(bpy)Cl₂], formation of bis‐oligonucleotide adducts was observed, whereas [Pt(bpy)(MeNH₂)Cl]⁺ gave monoadducts, with chloride ligands substituted in both cases. Neither in the dark nor under light irradiation was the reductive elimination process of these Pt^IV complexes accompanied by oxidative DNA damage. This work raises the question of the stability of photoactivatable Pt^IV complexes toward moderate heating conditions.     

Bis­[S‐methyl 3‐(2‐bromo­benzyl­idene)­di­thio­cab­aza­to‐N3,S]­platinum(II)

The Schiff base ligand in the title complex, [Pt(C₉H₈BrN₂S₂)₂], is deprotonated from its tautomeric thiol form and coordinated to Pt^IIvia the mercapto S and β–N atoms. The configuration about Pt^II is a perfect square‐planar, with two equivalent Pt—N [2.023 (3) Å] and Pt—S [2.293 (1) Å] bonds. The phenyl ring is twisted against the coordination moiety Pt1/N1/N1′/S2′/S2 by 31.8 (2)°, due to the steric hindrance induced by ortho‐substituted bulky Br atom.     

Palladium(II) Acetylide Complexes with Pincer‐Type Ligands: Photophysical Properties,Intermolecular Interactions,and Photo‐cytotoxicity

Two classes of cationic palladium(II) acetylide complexes containing pincer‐type ligands, 2,2′:6′,2′′‐terpyridine (terpy) and 2,6‐bis(1‐butylimidazol‐2‐ylidenyl)pyridine (C^N^C), were prepared and structurally characterized. Replacing terpy with the strongly σ‐donating C^N^C ligand with two N‐heterocyclic carbene (NHC) units results in the Pd^II acetylide complexes displaying phosphorescence at room temperature and stronger intermolecular interactions in the solid state. X‐ray crystal structures of [Pd(terpy)(C≡CPh)]PF₆ ( 1 ) and [Pd(C^N^C)(C≡CPh)]PF₆ ( 7 ) reveal that the complex cations are arranged in a one‐dimensional stacking structure with pair‐like Pd^II⋅⋅⋅Pd^II contacts of 3.349 Å for 1 and 3.292 Å for 7 . Density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT) calculations were used to examine the electronic properties. Comparative studies of the [Pt(L)(C≡CPh)]⁺ analogs by ¹H NMR spectroscopy shed insight on the intermolecular interactions of these Pd^II acetylide complexes. The strong Pd−C_carbene bonds render 7 and its derivative sufficiently stable for investigation of photo‐cytotoxicity under cellular conditions.     

Luminescent Cyclometalated Alkynylplatinum(II) Complexes with a Tridentate Pyridine‐Based N‐Heterocyclic Carbene Ligand: Synthesis,Characterization, Electrochemistry,Photophysics, and Computational Studies

A new class of luminescent alkynylplatinum(II) complexes with a tridentate pyridine‐based N‐heterocyclic carbene (2,6‐bis(1‐butylimidazol‐2‐ylidenyl)pyridine) ligand, [Pt^II(C^N^C)(C?CR)][PF₆], and their chloroplatinum(II) precursor complex, [Pt^II(C^N^C)Cl][PF₆], have been synthesized and characterized. One of the alkynylplatinum(II) complexes has also been structurally characterized by X‐ray crystallography. The electrochemistry, electronic absorption and luminescence properties of the complexes have been studied. Nanosecond transient absorption (TA) spectroscopy has also been performed to probe the nature of the excited state. The origin of the absorption and emission properties has been supported by computational studies.     

PtII Complexes with 6‐(5‐Trifluoromethyl‐Pyrazol‐3‐yl)‐2,2′‐Bipyridine Terdentate Chelating Ligands: Synthesis,Characterization, and Luminescent Properties

A series of Pt^II complexes Pt(fpbpy)Cl ( 1 ), Pt(fpbpy)(OAc) ( 2 ), Pt(fpbpy)(NHCOMe) ( 3 ), Pt(fpbpy)(NHCOEt) ( 4 ), and [Pt(fpbpy)(NCMe)](BF₄) ( 5 ) with deprotonated 6‐(5‐trifluoromethyl‐pyrazol‐3‐yl)‐2,2′‐bipyridine terdentate ligand are prepared, among which 1 is converted to complexes 2 – 5 by a simple ligand substitution. Alternatively, acetamide complex 3 is prepared by hydrolysis of acetonitrile complex 5 , while the back conversion from 3 to 1 is regulated by the addition of HCl solution, showing the reaction sequence 1 → 5 → 3 → 1 . Multilayer OLED devices are successfully fabricated by using triphenyl‐(4‐(9‐phenyl‐9H‐fluoren‐9‐yl)phenyl) silane (TPSi‐F) as host material and with doping concentrations of 1 varying from 7 to 100 %. The electroluminescence showed a substantial red‐shifting versus the normal photoluminescence detected in solution. Moreover, at a doping concentration of 28 %, the device showed a saturated red luminescence with a maximum external quantum yield of 8.5 % at 20 mA cm^?2 and a peak luminescence of 47 543 cd m^?2 at 18.5 V.     

π–π Dimerization of a mono(pyridyl–imine) platinum(II) chelate

The cation of the title complex salt, chlorido{2,2‐dimethyl‐N‐[(E)‐1‐(pyridin‐2‐yl)ethylidene]propane‐1,3‐diamine}platinum(II) tetrafluoridoborate, [PtCl(C₁₂H₁₉N₃)]BF₄, exhibits a nominally square‐planar Pt^II ion coordinated to a chloride ion [Pt—Cl = 2.3046 (9) Å] and three unique N‐atom types, viz. pyridine, imine and amine, of the tridentate Schiff base ligand formed by the 1:1 condensation of 1‐(pyridin‐2‐yl)ethanone and 2,2‐dimethylpropane‐1,3‐diamine. The cations are π‐stacked in inversion‐related pairs (dimers), with a mean plane separation of 3.426 Å, an intradimer Pt...Pt separation of 5.0785 (6) Å and a lateral shift of 3.676 Å. The centroid (Cg) of the pyridine ring is positioned approximately over the Pt^II ion of the neighbouring cation (Pt...Cg = 3.503 Å).     

Water‐Soluble Luminescent Cyclometalated Gold(III) Complexes with cis‐Chelating Bis(N‐Heterocyclic Carbene) Ligands: Synthesis and Photophysical Properties

A new class of cyclometalated Au^III complexes containing various bidentate C‐deprotonated C^N and cis‐chelating bis(N‐heterocyclic carbene) (bis‐NHC) ligands has been synthesized and characterized. These are the first examples of Au^III complexes supported by cis‐chelating bis‐NHC ligands. [Au(C^N)(bis‐NHC)] complexes display emission in solutions under degassed condition at room temperature with emission maxima (λ_max) at 498–633 nm and emission quantum yields of up to 10.1 %. The emissions are assigned to triplet intraligand (IL) π→π* transitions of C^N ligands. The Au^III complex containing a C^N (C‐deprotonated naphthalene‐substituted quinoline) ligand with extended π‐conjugation exhibits prompt fluorescence and phosphorescence of comparable intensity with λ_max at 454 and 611 nm respectively. With sulfonate‐functionalized bis‐NHC ligand, four water‐soluble luminescent Au^III complexes, including those displaying both fluorescence and phosphorescence, were prepared. They show similar photophysical properties in water when compared with their counterparts in acetonitrile. The long phosphorescence lifetime of the water‐soluble AuIII complex with C‐deprotonated naphthalene‐substituted quinoline ligand renders it to function as ratiometric sensor for oxygen. Inhibitory activity of one of these water‐soluble Au^III complexes towards deubiquitinase (DUB) UCHL3 has been investigated; this complex also displayed a significant inhibitory activity with IC₅₀ value of 0.15 μM .     

Highly Efficient Deep‐Blue Emitters Based on cis and trans N‐Heterocyclic Carbene PtII Acetylide Complexes: Synthesis,Photophysical Properties,and Mechanistic Studies

We have synthesized cis and trans N‐heterocyclic carbene (NHC) platinum(II) complexes bearing σ‐alkynyl ancillary ligands, namely [Pt(dbim)₂(C?CR)₂] [DBIM=N,N′‐didodecylbenzimidazoline‐2‐ylidene; R=C₆H₄F ( 4 ), C₆H₅ ( 5 ), C₆H₂(OMe)₃ ( 6 ), C₄H₃S ( 7 ), and C₆H₄C?CC₆H₅ ( 8 )] and [Pt(ibim)₂(C?CC₆H₅)₂] ( 9 ) (ibim=N,N′‐diisopropylbenzimidazoline‐2‐ylidene), starting from [Pt(cod)(C?CR)₂] (COD=cyclooctadiene) and 2 equivalents of [dbimH]Br ([ibimH]Br for complexes 9 ) in the presence of tBuOK and THF. Mechanistic investigations aimed at uncovering the cis to trans isomerization reaction have been performed on the representative cis complex 5 a [Pt(dbim)₂(C?CC₆H₅)₂] and revealed the isomerization to progress smoothly in good yield when 5 a was treated with catalytic amounts of [Pt(cod)(C?CR)₂] at 75 °C in THF or when 5 a was heated at 200 °C in the solid state under an inert atmosphere. Detailed examination of the reactions points to the possible involvement, in a catalytic fashion, of a solvent‐stabilized Pt^II dialkyne complex in the former case and a Pt⁰ NHC complex in the latter case, for the transformation of the cis isomer to the corresponding trans complex. Thermal stability and the isomerization process in the solid state have been further investigated on the basis of TGA and DSC measurements. X‐ray diffraction studies have been carried out to confirm the solid‐state structures of 4 b , 5 a , 5 b , and 9 b . All of the synthesized dialkyne complexes 4 – 9 exhibit phosphorescence in solution, in the solid state at room temperature (RT), and also in frozen solvent glasses at 77 K. The emission wavelengths and quantum yields have been found to be highly tunable as a function of the alkynyl ligand. In particular, the trans isomer of complex 9 in a spin‐coated film (10 wt % in poly(methyl methacrylate), PMMA) exhibits a high phosphorescence quantum yield of 80 %, which is the highest reported for Pt^II‐based deep‐blue emitters. Experimental observations and time‐dependent density functional theory (TD‐DFT) calculations are strongly indicative of the emission being mainly governed by metal‐perturbed interligand (³IL) charge transfer.     

Cyclometalated Ruthenium(II) Complexes Featuring Tridentate Click‐Derived Ligands for Dye‐Sensitized Solar Cell Applications

A series of heteroleptic bis(tridentate) Ru^II complexes featuring N^C^N‐cyclometalating ligands is presented. The 1,2,3‐triazole‐containing tridentate ligands are readily functionalized with hydrophobic side chains by means of click chemistry and the corresponding cyclometalated Ru^II complexes are easily synthesized. The performance of these thiocyanate‐free complexes in a dye‐sensitized solar cell was tested and a power conversion efficiency (PCE) of up to 4.0 % (J_sc=8.1 mA cm^?2, V_oc=0.66 V, FF=0.70) was achieved, while the black dye ((NBu₄)₃[Ru(Htctpy)(NCS)₃]; Htctpy=2,2′:6′,2′′‐terpyridine‐4′‐carboxylic acid‐4,4′′‐dicarboxylate) showed 5.2 % (J_sc=10.7 mA cm^?2, V_oc=0.69 V, FF=0.69) under comparable conditions. When co‐adsorbed with chenodeoxycholic acid, the PCE of the best cyclometalated dye could be improved to 4.5 % (J_sc=9.4 mA cm^?2, V_oc=0.65 V, FF=0.70). The PCEs correlate well with the light‐harvesting capabilities of the dyes, while a comparable incident photon‐to‐current efficiency was achieved with the cyclometalated dye and the black dye. Regeneration appeared to be efficient in the parent dye, despite the high energy of the highest occupied molecular orbital. The device performance was investigated in more detail by electrochemical impedance spectroscopy. Ultimately, a promising Ru^II sensitizer platform is presented that features a highly functionalizable “click”‐derived cyclometalating ligand.     

Design of Luminescent,Heteroleptic, Cyclometalated PtII and PtIV Complexes: Photophysics and Effects of the Cyclometalated Ligands

Neutral pentafluorophenyl benzoquinolinyl Pt^II [Pt(bzq)(HC^N−κN)(C₆F₅)] ( 1 a – g ) complexes, bearing nonmetalated N-heterocyclic HC^N ligands [HC^N=2,5-diphenyl-1,3,4-oxadiazole (Hoxd) a , 2-(2,4-difluorophenyl)pyridine (dfppy) b , 2-phenylbenzo[d]thiazole (pbt) c , 2-(4-bromophenyl)benzo[d]thiazole (Br-pbt) d , 2-phenylquinoline (pq) e , 2-thienylpyridine (thpy) f , 1-(2-pyridyl)pyrene (pypy) g ], and heteroleptic bis(cyclometalated) Pt^IV fac-[Pt(bzq)(C^N)(C₆F₅)Cl] ( 2 b – g , bzq: benzo[h]quinolinyl) derivatives, generated by oxidation of 1 b – g with PhICl₂, are reported. The oxidation reaction of 1 a evolved with formation of the bimetallic Pt^IV complex syn-[Pt(bzq)(C₆F₅)Cl(μ-OH)]₂ 3 . The crystal structures of 1 a,d,f , 2 b,d,e and 3 were corroborated by X-ray crystallography. A comparative study of the absorption and photoluminescence properties of the two series of complexes Pt^II ( 1 ) and Pt^IV ( 2 ), supported by time-dependent DFT calculations (TD-DFT), is presented. The low-lying transitions (absorption and emission) of Pt^II complexes 1 a – e [solution and polystyrene (PS) films] were assigned to the IL/MLCT mixture located on the cyclometalated Pt(bzq) unit, with minor IL′/ML′CT/LL′CT contributions involving the non-metalated ligand. Complex 1 g , bearing the more delocalized pyridyl pyrene (Hpypy) as an ancillary ligand, shows dual ¹ππ* and ³ππ* (Hpypy) emission in fluid CH₂Cl₂ and dual ³IL/³MLCT [Pt(bzq)] and [³ππ*, Hpypy] phosphorescence at 77 K. Upon oxidation, Pt^IV complexes 2 b – f display (solution, PS) ligand-based phosphorescence that arises from the bzq in 2 b (³LC) or from the second C^N ligand in 2 c – f (³L′C) with some ³LL′CT in 2 f . Despite metalation of the pyrenyl group, 2 g exhibits dual emission ¹ππ*/³ππ* located on the pypy chromophore.     

The Role of Substituent Effects in Tuning Metallophilic Interactions and Emission Energy of Bis‐4‐(2‐pyridyl)‐1,2,3‐triazolatoplatinum(II) Complexes

The photoluminescence spectra of a series of 5‐substituted pyridyl‐1,2,3‐triazolato Pt^II homoleptic complexes show weak emission tunability (ranging from λ=397–408 nm) in dilute (10^?6 M ) ethanolic solutions at the monomer level and strong tunability in concentrated solutions (10^?4 M ) and thin films (ranging from λ=487–625 nm) from dimeric excited states (excimers). The results of density functional calculations (PBE0) attribute this “turn‐on” sensitivity and intensity in the excimer to strong Pt–Pt metallophilic interactions and a change in the excited‐state character from singlet metal‐to‐ligand charge transfer (¹MLCT) to singlet metal‐metal‐to‐ligand charge transfer (¹MMLCT) emissions in agreement with lifetime measurements.     

trans‐Dichloro(dimethyl sulfide‐κS)(pyridine‐κN)platinum(II)

The structure of the title compound, [PtCl₂(C₅H₅N)(C₂H₆S)], consists of discrete mol­ecules in which the Pt‐atom coordination is slightly distorted square planar. The Cl atoms are trans to each other, with a Cl—Pt—Cl angle of 176.60 (7)°. The pyridine ligand is rotated 64.5 (2)° from the Pt square plane and one of the Pt—Cl bonds essentially bisects the C—S—C angle of the di­methyl sulfide ligand. In the crystal structure, there are extensive weak C—H⋯Cl interactions, the shortest of which connects mol­ecules into centrosymmetric dimers. A comparison of the structural trans influence on Pt—S and Pt—­N distances for PtS(CH₃)₂ and Pt(pyridine) fragments, respectively, in square‐planar Pt^II complexes is presented.     

Near Infrared Phosphorescent,Non‐oxidizable Palladium and Platinum Perfluoro‐phthalocyanines

New Pd^II and Pt^II complexes with a highly electron‐deficient ligand (H₂PcF₆₄) were conveniently prepared in a three‐step synthesis. This is the first time that the phosphorescence of phthalocyanines with a H₂PcF₆₄ framework has been measured. Based on these measurements, the triplet‐state energies (E_T) were directly determined. Transient absorption experiments revealed broad T₁→T_n absorption spanning from ca. 350 to ca. 1000 nm and allowed determination of the triplet‐state lifetimes. Removal of the Pd or Pt from the perfluoro‐phthalocyanine resulted in a significant increase of the triplet lifetime for H₂PcF₆₄. The very efficient intersystem crossing observed for both PdPcF₆₄ and PtPcF₆₄ leads to residual fluorescence and suppresses the fluorescence lifetimes to less than 50 ps. The absence of Pd and Pt in the perfluoro‐phthalocyanine ligand, viz. H₂PcF₆₄, led to a recovery of fluorescence. Cyclic voltamperometry studies pointed to complete resistance of PdPcF₆₄ and PtPcF₆₄ to oxidation and very strong electron affinity, which rendered these materials very good electron acceptors (n‐type materials). The presence of d‐orbital metals such as Pd^II and Pt^II in the phthalocyanine ring stabilizes their reduced forms, as indicated by the spectroelectrochemical experiments. PdPcF₆₄ and PtPcF₆₄ easily sensitize singlet oxygen production with very high quantum yields. Both phthalocyanines presented resistance to photodegradation in the solid state under aerobic conditions and under intense irradiation.     

Luminescent Pincer Platinum(II) Complexes with Emission Quantum Yields up to Almost Unity: Photophysics,Photoreductive CC Bond Formation,and Materials Applications

Luminescent pincer‐type Pt^II complexes supported by C‐deprotonated π‐extended tridentate R? C^N^N? R′ ligands and pentafluorophenylacetylide ligands show emission quantum yields up to almost unity. Femtosecond time‐resolved fluorescence measurements and time‐dependent DFT calculations together reveal the dependence of excited‐state structural distortions of [Pt(R? C^N^N? R′)(C?C‐C₆F₅)] on the positional isomers of the tridentate ligand. Pt complexes [Pt(R‐C^N^N? R′)(C?C‐Ar)] are efficient photocatalysts for visible‐light‐induced reductive C? C bond formation. The [Pt(R‐C^N^N? R′)(C?C‐C₆F₅)] complexes perform strongly as phosphorescent dopants for green‐ and red‐emitting organic light‐emitting diodes (OLEDs) with external quantum efficiency values over 22.1 %. These complexes are also applied in two‐photon cellular imaging when incorporated into mesoporous silica nanoparticles (MSNs).     

The Challenge of Deciphering Linkage Isomers in Mixtures of Oligomeric Complexes Derived from 9‐Methyladenine and trans‐(NH3)2PtII Units

Metal coordination to N9‐substituted adenines, such as the model nucleobase 9‐methyladenine (9MeA), under neutral or weakly acidic pH conditions in water preferably occurs at N1 and/or N7. This leads, not only to mononuclear linkage isomers with N1 or N7 binding, but also to species that involve both N1 and N7 metal binding in the form of dinuclear or oligomeric species. Application of a trans‐(NH₃)₂Pt^II unit and restriction of metal coordination to the N1 and N7 sites and the size of the oligomer to four metal entities generates over 50 possible isomers, which display different feasible connectivities. Slowly interconverting rotamers are not included in this number. Based on ¹H NMR spectroscopic analysis, a qualitative assessment of the spectroscopic features of N1,N7‐bridged species was attempted. By studying the solution behavior of selected isolated and structurally characterized compounds, such as trans‐[PtCl(9MeA‐N7)(NH₃)₂]ClO₄ ? 2H₂O or trans,trans‐[{PtCl(NH₃)₂}₂(9MeA‐N1,N7)][ClO₄]₂ ? H₂O, and also by application of a 9MeA complex with an (NH₃)₃Pt^II entity at N7, [Pt(9MeA‐N7)(NH₃)₃][NO₃]₂, which blocks further cross‐link formation at the N7 site, basic NMR spectroscopic signatures of N1,N7‐bridged Pt^II complexes were identified. Among others, the trinuclear complex trans‐[Pt(NH₃)₂{μ‐(N1‐9MeA‐N7)Pt(NH₃)₃}₂][ClO₄]₆ ? 2H₂O was crystallized and its rotational isomerism in aqueous solution was studied by NMR spectroscopy and DFT calculations. Interestingly, simultaneous Pt^II coordination to N1 and N7 acidifies the exocyclic amino group of the two 9MeA ligands sufficiently to permit replacement of one proton each by a bridging heterometal ion, Hg^II or Cu^II, under mild conditions in water.     

Platinum‐Containing Polyoxometalates: syn‐ and anti‐[PtII2(α‐PW11O39)2]10− and Formation of the Metal–Metal‐Bonded di‐PtIII Derivatives

The first examples of dimeric, di‐Pt^II‐containing heteropolytungstates are reported. The two isomeric di‐platinum(II)‐containing 22‐tungsto‐2‐phosphates [anti‐Pt^II₂(α‐PW₁₁O₃₉)₂]^10? ( 1 a ) and [syn‐Pt^II₂(α‐PW₁₁O₃₉)₂]^10? ( 2 a ) were synthesized in aqueous pH 3.5 medium using one‐pot procedures. Polyanions 1 a and 2 a contain a core comprising two face‐on PtO₄ units, with a Pt???Pt distance of 2.9–3 Å. Both polyanions were investigated by single‐crystal XRD, IR, TGA, UV/Vis, ³¹P NMR, ESI‐MS, CID‐MS/MS, electrochemistry, and DFT. On the basis of DFT and electrochemistry, we demonstrated that the {Pt₂^II} moiety in 1 a and 2 a can undergo fully reversible two‐electron oxidation to {Pt₂^III}, accompanied by formation of a single Pt?Pt bond. Hence we have discovered the novel subclass of Pt^III‐containing heteropolytungstates.     

Cyano‐Bridged ‘Oximato’ Complexes: Synthesis,Structure, and Catalase‐Like Activities

The reaction of the ‘oximato’‐ligand precursor A (Fig. 1) and metal salts with KCN gave two mononuclear complexes [ML(CN)(H₂O)_n](ClO₄) ( 1 and 2 ; L={N‐(hydroxy‐κO)‐α‐oxo‐N′‐[(pyridin‐2‐yl‐κN)methyl[1,1′‐biphenyl]‐4‐ethanimidamidato‐κN′}; M=Co^II ( 1 ), Cu^II ( 2 ); n=2 for Co^II, n=0 for Cu^II; Figs. 2 and 3). The new cyano‐bridged pentanuclear ‘oximato’ complexes [{ML(H₂O)_n(NC)}₄M¹(H₂O)_x](ClO₄)₂ ( 3 – 6 ) and trinuclear complexes [{ML(H₂O)_n(NC)}₂M¹L](ClO₄) ( 7 – 10 ) ([M¹=Mn^II, Cu^II; x=2 for Mn^II, x=0 for Cu^II] were synthesized from mononuclear complexes and characterized by elemental analyses, magnetic susceptibility, molar conductance, and IR and thermal analysis. The four [ML(CN)(H₂O)_n]⁺ moieties are connected by a metal(II) ion in the pentanuclear complexe 3 – 6 , each one involving four cyano bridging ligands (Fig. 4). The central metal ion displays a square‐planar or octahedral geometry, with the cyano bridging ligands forming the equatorial plane. The axial positions are occupied by two aqua ligands in the case of the central Mn‐atom. The two [ML(CN)(H₂O)_n]⁺ moieties and an ‘oximato’ ligand are connected by a metal(II) ion in the trinuclear complexes 7 – 10 , each one involving two cyano bridging ligands (Fig. 5). The central metal ions display a distorted square‐pyramidal geometry, with two cyano bridging ligands and the donor atoms of the tridentate ‘oximato’ ligand. Moreover catalytic activities of the complexes for the disproportionation of hydrogen peroxide (H₂O₂) were also investigated in the presence of 1H‐imidazole. The synthesized homopolynuclear Cu^II complexes 6 and 10 displayed eficiency in disproportion reactions of H₂O₂ producing H₂O and dioxygen thus showing catalase‐like activity.     

Synthesis,Structures and Spectroscopic Properties of Platinum(II), Palladium(II) and Copper(I) Halide Complexes with Pyrimidine‐phosphine Ligand

The reactions of pyrimidine‐phosphine ligand N‐[(diphenylphosphino)methyl]‐2‐pyrimidinamine ( L ) with various metal salts of Pt^II, Pd^II and Cu^I provide three new halide metal complexes, Pt₂Cl₄(μ‐L)₂·2CH₂Cl₂ ( 1 ), Pd₂Cl₄(μ‐L)₂ ( 2 ), and [Cu₂(μ‐I)₂L₂]_n ( 3 ). Single crystal X‐ray diffraction studies show that complexes 1 and 2 display a similar bimetallic twelve‐membered ring structure, while complex 3 consists of one‐dimensional polymeric chains, which are further connected into a 2‐D supramolecular framework through hydrogen bonds. In the binuclear complexes 1 and 2 , the ligand L serves as a bridge with the N and P as coordination atoms, but in the polymeric complex 3 , both bridging and chelating modes are adopted by the ligand. The spectroscopic properties of complexes 1 ‐ 3 as well as L have been investigated, in which complex 3 exhibits intense photoluminescence originating from intraligand charge transfer (ILCT) π→π* and metal‐to‐ligand charge‐transfer (MLCT) excited states both in acetonitrile solution and solid state, respectively.