Poly[[trans‐diaquabis(μ2‐biphenyl‐2,2′‐dicarboxylato)bis(μ2‐4,4′‐bipyridine)dicobalt(II)] biphenyl‐2,2′‐dicarboxylic acid disolvate]

In the title compound, {[Co₂(C₁₄H₈O₄)₂(C₁₀H₈N₂)₂(H₂O)₂]·2C₁₄H₁₀O₄}_n, each Co^II ion is six‐coordinate in a slightly distorted octahedral geometry. Both Co^II ions are located on twofold axes. One is surrounded by two O atoms from two biphenyl‐2,2′‐dicarboxylate (dpa) dianions, two N atoms from two 4,4′‐bipyridine (bpy) ligands and two water molecules, while the second is surrounded by four O atoms from two dpa dianions and two N atoms from two bpy ligands. The coordinated dpa dianion functions as a κ³‐bridge between the two Co^II ions. One carboxylate group of a dpa dianion bridges two adjacent Co^II ions, and one O atom of the other carboxylate group also chelates to a Co^II ion. The Co^II ions are bridged by dpa dianions and bpy ligands to form a chiral sheet. There are several strong intermolecular hydrogen bonds between the H₂dpa solvent molecule and the chiral sheet, which result in a sandwich structure.     

A one‐dimensional iodine‐bridged PtII/PtIV mixed‐valence complex,catena‐poly[[[bis­(ethyl­ene­diamine)­platinum(II)]‐μ‐iodo‐[bis­(ethyl­ene­di­amine)platinum(IV)]‐μ‐iodo] hydrogenphosphate dihydrogenphosphate iodide trihydrate]

The title compound, {[Pt^IIPt^IVI₂(C₂H₈N₂)₄](HPO₄)(H₂PO₄)I·3H₂O}_n, has a chain structure composed of square‐planar [Pt(en)₂]²⁺ and elongated octa­hedral trans‐[PtI₂(en)₂]²⁺ cations (en is ethyl­ene­diamine) stacked alternately along the c axis and bridged by the I atoms; a three‐dimensionally valence‐ordered system exists with respect to the Pt sites. The title compound also has a unique cyclic tetra­mer structure composed of two hydrogenphosphate and two dihydrogenphosphate ions connected by strong hydrogen bonds [O⋯O = 2.522 (10), 2.567 (10) and 2.569 (11) Å]. The Pt and I atoms form a zigzag ⋯I—Pt^IV—I⋯Pt^II⋯ chain, with Pt^IV—I bond distances of 2.6997 (7) and 2.6921 (7) Å, inter­atomic Pt^II⋯I distances of 3.3239 (8) and 3.2902 (7) Å, and Pt^IV—I⋯Pt^II angles of 154.52 (3) and 163.64 (3)°. The structural parameters indicating the mixed‐valence state of platinum, expressed by δ = (Pt^IV—I)/(Pt^II—I), are 0.812 and 0.818 for the two independent I atoms.     

A Nitroxide‐Tagged Platinum(II) Complex Enables the Identification of a DNA G‐Quadruplex Binding Mode

We reported a novel strategy for investigating small molecule binding to G‐quadruplexes (GQs). A newly synthesized dinuclear platinum(II) complex (Pt₂L) containing a nitroxide radical was shown to selectively bind a GQ‐forming sequence derived from human telomere (hTel). Using the nitroxide moiety as a spin label, electron paramagnetic resonance (EPR) spectroscopy was carried out to investigate binding between Pt₂L and hTel GQ. Measurements indicated that two molecules of Pt₂L bind with one molecule of hTel GQ. The inter‐spin distance measured between the two bound Pt₂L, together with molecular docking analyses, revealed that Pt₂L predominately binds to the neighboring narrow and wide grooves of the G‐tetrads as hTel adopts the antiparallel conformation. The design and synthesis of nitroxide tagged GQ binders, and the use of spin‐labeling/EPR to investigate their interactions with GQs, will aid the development of small molecules for manipulating GQs involved in crucial biological processes.     

A one‐dimensional chloride‐bridged PtII/PtIV mixed‐valence complex with a 4‐[(4‐hydroxyphenyl)diazenyl]benzenesulfonate counter‐ion

The title compound, catena‐poly[[[bis(ethylenediamine‐κ²N,N′)platinum(II)]‐ μ‐chlorido‐[bis(ethylenediamine)platinum(IV)]‐μ‐chlorido] tetrakis{4‐[(4‐hydroxyphenyl)diazenyl]benzenesulfonate} dihydrate], {[Pt^IIPt^IVCl₂(C₂H₈N₂)₄](HOC₆H₄N=NC₆H₄SO₃)₄·2H₂O}_n, has a linear chain structure composed of square‐planar [Pt(en)₂]²⁺ (en is ethylenediamine) and elongated octahedral trans‐[PtCl₂(en)₂]²⁺ cations stacked alternately, bridged by Cl atoms, along the b axis. The Pt atoms are located on an inversion centre, while the Cl atoms are disordered over two sites and form a zigzag ...Cl—Pt^IV—Cl...Pt^II... chain, with a Pt^IV—Cl bond length of 2.3140 (14) Å, an interatomic Pt^II...Cl distance of 3.5969 (15) Å and a Pt^IV—Cl...Pt^II angle of 170.66 (6)°. The structural parameter indicating the mixed‐valence state of the Pt atom, expressed by δ = (Pt^IV—Cl)/(Pt^II...Cl), is 0.643.     

Observation of the Properties of a Single Unit of a Limited CDW Structure in a PtII/PtIV Host–Guest Binary System Based on a Square‐Shaped Complex

A macrocyclic tetranuclear platinum(II) complex [Pt(en)(4,4′‐bpy)]₄(NO₃)₈ ( 1 ?(NO₃)₈; en=ethylenediamine, 4,4′‐bpy=4,4′‐bipyridine) and a mononuclear platinum(IV) complex [Pt(en)₂Br₂]Br₂ ( 2 ?Br₂) formed two kinds of Pt^II/Pt^IV mixed valence assemblies when reacted: a discrete host–guest complex 1 ? 2 ?Br₁₀ ( 3 ) and an extended 1‐D zigzag sheet 1 ?( 2 )₃?Br₈(NO₃)₆ ( 4 ). Single crystal X‐ray analysis showed that the dimensions of the assemblies could be stoichiometrically controlled. Resonance Raman spectra suggested the presence of an intervalence interaction, which is typically observed for quasi‐1‐D halogen‐bridged M^II/M^IV complexes. The intervalence interaction indicates the presence of an isolated {Pt^II???X? Pt^IV? X???Pt^II} moiety in the structure of 4 . On the basis of electronic spectra and polarized reflectance measurements, we conclude that 4 exhibits intervalence charge transfer (IVCT) bands. A Kramers–Kronig transformation was carried out to obtain an optical conductivity spectrum, and two sub‐bands corresponding to slightly different Pt^II–Pt^IV distances were observed.     

Nanoscale MnII‐Coordination Polymers for Cell Imaging and Heterogeneous Catalysis

A mixed ligand approach was exploited to synthesize a new series of Mn^II‐based coordination polymers (CPs), namely, CP1 {[Mn(μ‐dpa)(μ‐4,4′‐bp)]?MeOH}_∞, CP2 {[Mn₃(μ‐dpa)₃(2,2′‐bp)₂]}_∞, CP3 {[Mn₃(μ‐dpa)₃(1,10‐phen)₂]?2 H₂O}_∞, CP4 {[Mn(μ‐dpa)(μ‐4,4′‐bpe)_1.5]?H₂O}_∞, CP5 {[Mn₂(μ‐dpa)₂(μ‐4,4′‐bpe)₂]? DEF}_∞, and CP6 {[Mn(μ‐dpa)(μ‐4,4′‐bpe)_1.5]? DMA}_∞ (dpa=3,5‐dicarboxyphenyl azide, 2,2′‐bp=2,2′‐bipyridine, 1,10‐phen=1,10‐phenanthroline, 4,4′‐bpe=1,2‐bis(4‐pyridyl)ethylene, 4,4′‐bp=4,4′‐bipyridine, DEF=N,N‐diethylformamide, DMA=N,N‐dimethylacetamide), to develop multifunctional CPs. Various techniques, such as single‐crystal X‐ray diffraction (SXRD), FTIR spectroscopy, elemental analysis, and thermogravimetric analysis, were employed to fully characterize these CPs. The majority of the CPs displayed a four‐connected sql topology, whereas CP4 and CP6 exhibited a two‐dimensional SnS network architecture, which was further entangled in a polycatenation mode. Compound CP1 displayed an open framework structure. The CPs were scaled down to the nanoregime in a ball mill for cell imaging studies. Whereas CP2 and CP4 were employed for cell imaging with RAW264.7 cells, CP1 was exploited for both cell imaging and heterogeneous catalysis in a cyanosilylation reaction.     

Near‐Infrared‐III‐Absorbing and ‐Emitting Dyes: Energy‐Gap Engineering of Expanded Porphyrinoids via Metallation

The synthesis of organometallic complexes of modified 26π‐conjugated hexaphyrins with absorption and emission capabilities in the third near‐infrared region (NIR‐III) is described. Symmetry alteration of the frontier molecular orbitals (MOs) of bis‐Pd^II and bis‐Pt^II complexes of hexaphyrin via N‐confusion modification led to substantial metal d_π–p_π interactions. This MO mixing, in turn, resulted in a significantly narrower HOMO–LUMO energy gap. A remarkable long‐wavelength shift of the lowest S₀→S₁ absorption beyond 1700 nm was achieved with the bis‐Pt^II complex, t ‐Pt₂‐3 . The emergence of photoacoustic (PA) signals maximized at 1700 nm makes t ‐Pt₂‐3 potentially useful as a NIR‐III PA contrast agent. The rigid bis‐Pd^II complexes, t ‐Pd₂‐3 and c ‐Pd₂‐3 , are rare examples of NIR emitters beyond 1500 nm. The current study provides new insight into the design of stable, expanded porphyrinic dyes possessing NIR‐III‐emissive and photoacoustic‐response capabilities.     

A one‐dimensional platinum mixed‐valence complex with bridging thiocyanate S atoms: [[PtII(en)2](μ‐SCN)[PtIV(en)2](μ‐SCN)](ClO4)4 (en is ethane‐1,2‐diamine)

A new one‐dimensional platinum mixed‐valence complex with nonhalogen bridging ligands, namely catena‐poly[[[bis(ethane‐1,2‐diamine‐κ²N,N′)platinum(II)]‐μ‐thiocyanato‐κ²S:S‐[bis(ethane‐1,2‐diamine‐κ²N,N′)platinum(IV)]‐μ‐thiocyanato‐κ²S:S] tetrakis(perchlorate)], {[Pt₂(SCN)₂(C₂H₈N₂)₄](ClO₄)₄}_n, has been isolated. The Pt^II and Pt^IV atoms are located on centres of inversion and are stacked alternately, linked by the S atoms of the thiocyanate ligands, forming an infinite one‐dimensional chain. The Pt^IV—S and Pt^II...S distances are 2.3933 (10) and 3.4705 (10) Å, respectively, and the Pt^IV—S...Pt^II angle is 171.97 (4)°. The introduction of nonhalogen atoms as bridging ligands in this complex extends the chemical modifications possible for controlling the amplitude of the charge‐density wave (CDW) state in one‐dimensional mixed‐valence complexes. The structure of a discrete Pt^IV thiocyanate compound, bis(ethane‐1,2‐diamine‐κ²N,N′)bis(thiocyanato‐κS)platinum(IV) bis(perchlorate) 1.5‐hydrate, [Pt(SCN)₂(C₄H₈N₂)₂](ClO₄)₂·1.5H₂O, has monoclinic (C2) symmetry. Two S‐bound thiocyanate ligands are located in trans positions, with an S—Pt—S angle of 177.56 (3)°.     

A one‐dimensional coordination polymer based on a di‐Schiff base supported trinuclear CuII subunit

A novel one‐dimensional Cu^II coordination polymer, catena‐poly[bis(μ₄‐3‐{[2‐(3‐hydroxy‐2‐oxidobenzylidene)hydrazinylidene]methyl}benzene‐1,2‐diolato)dimethanoltricopper(II)], [Cu₃(C₁₄H₁₀N₂O₄)₂(CH₃OH)₂]_n, (I), was constructed with a di‐Schiff base supported centrosymmetric trinuclear Cu^II subunit. In the subunit, two peripheral symmetry‐related Cu^II cations have square‐pyramidal CuNO₄ geometry and the central third Cu^II cation lies on an inversion centre with octahedral CuN₂O₄ geometry. In (I), each partially deprotonated di‐Schiff base 3‐{[2‐(3‐hydroxy‐2‐oxidobenzylidene)hydrazinylidene]methyl}benzene‐1,2‐diolate ligand (Hbcaz³⁻) acts as a heptadentate ligand to bind the Cu^II centres into chains along the a axis. A centrosymmetric Cu₂O₂ unit containing an asymmetrically bridging O atom, being axial at one Cu atom and equatorial at the other Cu atom, links the trinuclear Cu^II subunit into a one‐dimensional chain, which is reinforced by intramolecular phenol–methanol O—H...O and methanol–phenolate O—H...O hydrogen bonds. Interchain π–π stacking interactions between pyrocatechol units, with a distance of 3.5251 (18) Å, contribute to the stability of the crystal packing.     

Structure‐Based Design of Platinum(II) Complexes as c‐myc Oncogene Down‐Regulators and Luminescent Probes for G‐Quadruplex DNA

A series of platinum(II) complexes with tridentate ligands was synthesized and their interactions with G‐quadruplex DNA within the c‐myc gene promoter were evaluated. Complex 1 , which has a flat planar 2,6‐bis(benzimidazol‐2‐yl)pyridine (bzimpy) scaffold, was found to stabilize the c‐myc G‐quadruplex structure in a cell‐free system. An in silico G‐quadruplex DNA model has been constructed for structure‐based virtual screening to develop new Pt^II‐based complexes with superior inhibitory activities. By using complex 1 as the initial structure for hit‐to‐lead optimization, bzimpy and related 2,6‐bis(pyrazol‐3‐yl)pyridine (dPzPy) scaffolds containing amine side‐chains emerge as the top candidates. Six of the top‐scoring complexes were synthesized and their interactions with c‐myc G‐quadruplex DNA have been investigated. The results revealed that all of the complexes have the ability to stabilize the c‐myc G‐quadruplex. Complex 3 a ([Pt^II L2R ] ⁺ ; L2 =2,6‐bis[1‐(3‐piperidinepropyl)‐1H‐enzo[d]imidazol‐2‐yl]pyridine, R =Cl) displayed the strongest inhibition in a cell‐free system (IC₅₀=2.2 μM ) and was 3.3‐fold more potent than that of 1 . Complexes 3 a and 4 a ([Pt^II L3R ]⁺; L3 =2,6‐bis[1‐(3‐morpholinopropyl)‐1H‐pyrazol‐3‐yl]pyridine, R =Cl) were found to effectively inhibit c‐myc gene expression in human hepatocarcinoma cells with IC₅₀ values of ≈17 μM , whereas initial hit 1 displayed no significant effect on gene expression at concentrations up to 50 μM . Complexes 3 a and 4 a have a strong preference for G‐quadruplex DNA over duplex DNA, as revealed by competition dialysis experiments and absorption titration; 3 a and 4 a bind G‐quadruplex DNA with binding constants (K) of approximately 10⁶–10⁷ dm³ mol^?1, which are at least an order of magnitude higher than the K values for duplex DNA. NMR spectroscopic titration experiments and molecular modeling showed that 4 a binds c‐myc G‐quadruplex DNA through an external end‐stacking mode at the 3′‐terminal face of the G‐quadruplex. Intriguingly, binding of c‐myc G‐quadruplex DNA by 3 b is accompanied by an increase of up to 38‐fold in photoluminescence intensity at λ_max=622 nm.     

Synthesis,Crystal Structure,and Characterization of Two Oxamido‐bridged NiIICuIINiII Heteronuclear Complexes

Two new trinuclear complexes [Cu^II(Ni^IIX₁)₂(C₂H₅OH)₂]· (ClO₄)₂·2(CH₃OH) ( 1 ) and [Cu^II(Ni^IIX₂)₂(H₂O)]·(ClO₄)₂· 0.75(H₂O) ( 2 ) (X₁ = dianion of 5,6;13,14‐dibenzo‐7,12‐bis(ethoxycarboxyl)‐9‐methyl‐2,3‐dioxo‐1,4,8,11‐tetraazacyclotetradeca‐7,11‐diene. X₂ = dianion of 5,6;13,14‐dibenzo‐9,10‐cyclohexano‐7,12‐bis(ethoxycarboxyl)‐2,3‐dioxo‐1,4,8,11‐tetraazacyclotetradeca7,11‐diene.) have been synthesized and characterized by single crystal X‐ray analysis, elemental analysis, IR, UV and EPR spectroscopies. The complexes consist of Ni^IICu^IINi^II heteronuclear cationic entities. The central Cu^II atom of 1 lies in an octahedral coordination environment, while that of 2 resides in a square‐pyramidal coordination sphere. The adjacent trinuclear units of 1 are linked together through π‐π stacking interactions resulting in a 1D supramolecular chain, whereas the π‐π stacking interactions between the contiguous units of 2 lead to a 2D structure. The EPR spectra of the two complexes show a signal of an axially elongated octahedral Cu^II system in 1 and an axially elongated square‐pyramidal Cu^II system in 2 , respectively. The hyperfine splitting of the Cu^II atoms (I^Cu = 3/2) has also been observed in the EPR spectra.     

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.     

Zinc(II) Complexes with 1H‐Imidazol‐4‐yl‐Containing Polyamine Ligand

The protonation and Zn^II/Cu^II complexation constants of tripodal polyamine ligand N¹‐(2‐aminoethyl)‐N¹‐(1H‐imidazol‐4‐ylmethyl)‐ethane‐1,2‐diamine (HL) were determined by potentiometric titration. Three new compounds, i.e. [H₃(HL)](ClO₄)₃ ( 5 ), [Zn(HL)Cl](ClO₄) ( 6 ) and {[Zn(L)](ClO₄)}_n ( 7 ) were obtained by reactions of HL · 4HCl with Zn(ClO₄)₂ · 6H₂O under different reaction pH, and they were compared with the corresponding Cu^II complexes reported previously. The results indicate that the reaction pH and metal ions have remarkable influence on the formation and structure of the complexes.     

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.     

Construction of Four Coordination Polymers based on 2‐[4‐(Pyridine‐4‐yl)phenyl]‐1H‐imidazole‐4,5‐dicarboxylic Acid

The imidazole‐based dicarboxylate ligand 2‐(4‐(pyridin‐4‐yl)phenyl)‐1H‐imidazole‐4,5‐dicarboxylic acid (H₃PyPhIDC), was synthesized and its coordination chemistry was studied. Solvothermal reactions of Ca^II, Mn^II, Co^II, and Ni^II ions with H₃PyPhIDC produced four coordination polymers, [Ca(μ₃‐HPyPhIDC)(H₂O)₂]_n ( 1 ), {[M₃(μ₂‐H₂PyPhIDC)₂(μ₃‐HPyPhIDC)₂₆(H₂O)₂] · 6H₂O}_n [M = Mn ( 2 ), Co ( 3 )], and {[Ni(μ₃‐HPyPhIDC)(H₂O)] · H₂O}_n ( 4 ). Compounds 1 – 4 were analyzed by IR spectroscopy, elemental analyses, and single‐crystal and powder X‐ray diffraction. Compound 1 displays a one‐dimensional (1D) infinite chain. Compounds 2 and 3 are of similar structure, showing 2D network structures with a (4,4) topology based on trinuclear clusters. Compound 4 has another type of 2D network structure with a 3‐connected (4.8²) topology. The results revealed that the structural diversity is attributed to the coordination numbers and geometries of metal ions as well as the coordination modes and conformations of H₃PyPhIDC. Moreover, the thermogravimetric analyses of all the compounds as well as luminescence properties of the H₃PyPhIDC ligand and compound 1 were also studied.     

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.     

Organoplatinum‐Substituted Polyoxometalate Inhibits β‐amyloid Aggregation for Alzheimer's Therapy

Aggregated β‐amyloid (Aβ) is widely considered as a key factor in triggering progressive loss of neuronal function in Alzheimer's disease (AD), so targeting and inhibiting Aβ aggregation has been broadly recognized as an efficient therapeutic strategy for curing AD. Herein, we designed and prepared an organic platinum‐substituted polyoxometalate, (Me₄N)₃[PW₁₁O₄₀(SiC₃H₆NH₂)₂PtCl₂] (abbreviated as Pt^II‐PW₁₁) for inhibiting Aβ₄₂ aggregation. The mechanism of inhibition on Aβ₄₂ aggregation by Pt^II‐PW₁₁ was attributed to the multiple interactions of Pt^II‐PW₁₁ with Aβ₄₂ including coordination interaction of Pt²⁺ in Pt^II‐PW₁₁ with amino group in Aβ₄₂, electrostatic attraction, hydrogen bonding and van der Waals force. In cell‐based assay, Pt^II‐PW₁₁ displayed remarkable neuroprotective effect for Aβ₄₂ aggregation‐induced cytotoxicity, leading to increase of cell viability from 49 % to 67 % at a dosage of 8 μm . More importantly, the Pt^II‐PW₁₁ greatly reduced Aβ deposition and rescued memory loss in APP/PS1 transgenic AD model mice without noticeable cytotoxicity, demonstrating its potential as drugs for AD treatment.     

Ylidyl‐substituted Phosphonio‐benzophospholides as Chelating Ligands

Phosphonio‐benzo[c]phospholides with an additional phosphonium ylide substituent in 3‐position were synthesized by deprotonation of appropriately substituted 1, 3‐bis‐phosphonio benzophospholide cations and characterized by spectroscopic and analytical data. The ability of these molecules to act as bidentate P, C‐chelating ligands to transition metal atoms was demonstrated in the reactions with [W(CO)₄(norbornadiene)] and [MCl₂(cyclooctadiene)] (M = Pd, Pt). The Pd^II and Pt^II complexes are distinguished by a strong inclination towards addition of H₂O to the 10π‐electron system of the ligand. The molecular structures of a W⁰ complex with a P, C‐chelating ylidyl‐phosphonio‐benzophospholide ligand and of the product resulting from H₂O‐addition to a corresponding Pt^II complex were determined. The structural parameters of the W⁰ complex provide evidence for the presence of substantial steric strain around the metal atom.     

Construction of Mononuclear Copper(II) and Trinuclear Cobalt(II) Complexes Based on Asymmetric Salamo‐Type Ligands

Mononuclear copper(II) and trinuclear cobalt(II) complexes, namely [Cu(L¹)]₂ · CH₂Cl₂ and [{Co(L²)(EtOH)}₂Co(H₂O)] · EtOH {H₂L¹ = 4,6‐dichloro‐6′‐methyoxy‐2,2′‐[1,1′‐(ethylenedioxydinitrilo)dimethylidyne]diphenol and H₃L² = 6‐ethyoxy‐6′‐hydroxy‐2,2′‐[1,1′‐(ethylenedioxydinitrilo)dimethylidyne]diphenol}, were synthesized and characterized by elemental analyses, IR and UV/Vis spectroscopy, and single‐crystal X‐ray diffraction. In the Cu^II complex, the Cu^II atom is four‐coordinate, with a N₂O₂ coordination sphere, and has a slightly distorted square‐planar arrangement. Interestingly, the obtained trinuclear Co^II complex is different from the common reported 2:3 (L:Co^II) salamo‐type Co^II complexes. Infinite 2D layer supramolecular structures are formed via abundant intermolecular hydrogen bonding and π ··· π stacking interactions in the Cu^II and Co^II complexes.     

Synthesis and characterization of two one‐dimensional CdII coordination polymers (CPs) with 5‐amino‐2,4,6‐tribromoisophthalic acid and flexible N‐donor bipyridyl ligands

The bromo‐substituted aromatic dicarboxylic acid 5‐amino‐2,4,6‐tribromoisophthalic acid (H₂ATBIP) was used to assemble with Cd^II ions in the presence of the N‐donor flexible bipyridyl ligands 3,3′‐(diazene‐1,2‐diyl)dipyridine (mzpy) and 1,3‐bis(pyridin‐3‐ylmethyl)urea (3bpmu), leading to the formation of two chain coordination polymers by adopting solution methods, namely, catena‐poly[[[triaqua(5‐amino‐2,4,6‐tribromoisophthalato‐κO)cadmium(II)]‐μ‐3,3′‐(diazene‐1,2‐diyl)dipyridine‐κ²N¹:N^1′] dihydrate], {[Cd(C₈H₂Br₃NO₄)(C₁₀H₈N₄)(H₂O)₃]·2H₂O}_n or {[Cd(ATBIP)(mzpy)(H₂O)₃]·2H₂O}_n, ( 1 ), and catena‐poly[[[tetraaquacadmium(II)]‐μ‐1,3‐bis(pyridin‐3‐ylmethyl)urea‐κ²N¹:N^1′‐[diaquabis(5‐amino‐2,4,6‐tribromoisophthalato‐κO)cadmium(II)]‐μ‐1,3‐bis(pyridin‐3‐ylmethyl)urea‐κ²N¹:N^1′] octahydrate], {[Cd(C₈H₂Br₃NO₄)(C₁₂H₁₂N₄O)(H₂O)₃]·4H₂O}_n or {[Cd(ATBIP)(3bpmu)(H₂O)₃]·4H₂O}_n, ( 2 ). Both complexes were characterized by FT–IR spectroscopic analysis, thermogravimetric analysis (TGA), solid‐state diffuse reflectance UV–Vis spectroscopic analysis, and single‐crystal and powder X‐ray diffraction analysis (PXRD). The mzpy and 3bpmu ligands bridge the Cd^II metal centres in ( 1 ) and ( 2 ) into one‐dimensional chains, and the ATBIP²⁻ ligands show a monodentate coordination to the Cd^II centres in both coordination polymers. A discrete water tetramer exists in ( 1 ). Within the chains of ( 1 ) and ( 2 ), there are halogen bonds between adjacent ATBIP²⁻ and mzpy or 3bpmu ligands, as well as hydrogen bonds between the ATBIP²⁻ ligands and the coordinated water molecules. With the aid of weak interactions, the structures of ( 1 ) and ( 2 ) are further extended into three‐dimensional supramolecular networks. An analysis of the solid‐state diffuse reflectance UV–Vis spectra of ( 1 ) and ( 2 ) indicates that a wide indirect band gap exists in both complexes. Complexes ( 1 ) and ( 2 ) exhibit irreversible and reversible dehydration–rehydration behaviours, respectively, and the solid‐state fluorescence properties of both complexes have been studied.