Formation,Dynamic Behavior,and Chemical Transformation of Pt Complexes with a Rotaxane‐like Structure

The reaction of [Pt(CH₂COMe)(Ph)(cod)] (cod=1,5‐cyclooctadiene) with (ArCH₂NH₂CH₂‐C₆H₄COOH)⁺(PF₆)^? (Ar=4‐tBuC₆H₄ or 9‐anthryl) in the presence of cyclic oligoethers such as dibenzo[24]crown‐8 (DB24C8) and dicyclohexano[24]crown‐8 (DC24C8) produces {(ce)[ArCH₂NH₂CH₂C₆H₄COOPt(Ph)(cod)]}⁺(PF₆)^? (ce=DB24C8 or DC24C8, Ar=4‐tBuC₆H₄ or 9‐anthryl) with interlocked structures. FABMS and NMR spectra of a solution of these compounds indicate that the Pt complexes with a secondary ammonium group and DB24C8 (or DC24C8) make up the axis and cyclic components, respectively. Temperature‐dependent ¹H NMR spectra of a solution of {(DB24C8)[4‐tBuC₆H₄CH₂NH₂CH₂‐C₆H₄COOPt(Ph)(cod)]}⁺(PF₆)^? ({(DB24C8)[ 4 ‐H]}⁺(PF₆)^?) show equilibration with free DB24C8 and the axis component. The addition of DB24C8 to a solution of {(DC24C8)[ 4 ‐H]}⁺(PF₆)^? causes partial exchange of the macrocyclic component of the interlocked molecules, giving a mixture of {(DC24C8)[ 4 ‐H]}⁺(PF₆)^?, {(DB24C8)[ 4 ‐H]}⁺(PF₆)^?, and free macrocyclic compounds. The reaction of 3,5‐Me₂C₆H₃COCl with {(DB24C8)[ 4 ‐H]}⁺(PF₆)^? affords the organic rotaxane {(DB24C8)(4‐tBuC₆H₄CH₂NH₂CH₂‐C₆H₄COOCOC₆H₃Me₂‐3,5)}⁺(PF₆)^? through C? O bond formation between the aroyl group and the carboxylate ligand of the axis component. The addition of 2,2′‐bipyridine (bpy) to a solution of {(DB24C8)[ 4 ‐H]}⁺(PF₆)^? induces the degradation of the interlocked structure to form a complex with trigonal bipyramidal coordination, [Pt(Ph)(bpy)(cod)]⁺(PF₆)^?, whereas the reaction of bpy with [Pt(OCOC₆H₄Me‐4)(Ph)(cod)] produces the square‐planar complex [Pt(OCOC₆H₄Me‐4)(Ph)(bpy)].     

Experimental and theoretical studies on the magnetic properties of manganese(II) compounds with mixed isocyanate and carboxylate bridges

Two manganese(II) isocyanate complexes with different flexible zwitterionic dicarboxylate ligands, [Mn(2)(bcpp)(NCO)(4)](n) (1; bcpp=1,3-bis(N-carboxylatomethyl-4-pyridinio)propane) and [Mn(2)(bcp)(NCO)(4)](n) (2; bcp=bis(N-carboxylatomethyl)-4,4'-bipyridinium, have been synthesized and characterized by X-ray crystallography and magnetic measurements. Both compounds consist of two-dimensional coordination layers in which uniform anionic chains with mixed (NCO)(2)(COO) triple bridges are cross-linked by flexible cationic 4,4'-trimethylenedipyridinium spacers. Magnetic studies revealed antiferromagnetic interactions through the triple bridges (J=-8.0 cm(-1) (1) and J=-8.6 cm(-1) (2)), which are stronger than those in the isoelectronic analogue (N(3))(2)(COO). To complement the experimental data, periodic and finite-cluster DFT and CASPT2 calculations were performed on the dimeric units of the (NCO)(2)(COO) and (N(3))(2)(COO) mixed-bridged systems to support the Heisenberg picture and stress the relative efficiency of the magnetic couplers. It was found that the isocyanate ligand plays a greater role in the conveyance of antiferromagnetic behavior than the azide counterpart, and that both pseudohalide bridges function cooperatively with the carboxylate group.     

Design,synthesis and in vitro cytotoxicity of novel dinuclear platinum(II) complexes with a tetradentate carrier ligand

Four novel dinuclear platinum complexes with a tetradentate ligand, (1R,1′R,2R,2′R)‐N¹,N^1′‐(1,2‐phenylenebis(methylene))dicyclohexane‐1,2‐diamine, as the carrier group, have been designed, synthesized and characterized, and their in vitro cytotoxicity against HepG‐2, A549, HCT‐116 and MCF‐7 cell lines evaluated using MTT assay. Results indicate that the targeted dinuclear platinum complexes H1 , H2 , H3 , H4 exhibit significant growth inhibitory properties against HepG‐2, A549 and HCT‐116 cell lines, but none of them show activity against MCF‐7 cell line. Compound H4 shows better antitumor activity than carboplatin against HepG‐2, A549 and HCT‐116 cell lines. Copyright © 2015 John Wiley & Sons, Ltd.     

The evolution of [[Ph2P(CH2)nPPh2]Pt(mu-S)2Pt[Ph2P(CH2)nPPh2]] (n=2, 3) metalloligands in protic acids: a cascade of sequential reactions

Given the nucleophilicity of the [Pt(2)S(2)] ring, the evolution of [Pt(2)(mu-S)(2)(P intersection P)(2)] (P intersection P=1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp)) metalloligands in the presence of the simplest electrophilic species, the proton, has been studied. Combined use of experimental and theoretical data has allowed the whole set of reactions ensuing the protonation of the [Pt(2)S(2)] core to be established. The titration of [Pt(2)(mu-S)(2)(P intersection P)(2)] with HCl or HClO(4) was monitored mainly by (31)P[(1)H] NMR and mass techniques. Characterization of all the species involved was completed with the determination of the crystal structure of [Pt(SH)(2)(P intersection P)], for dppe and dppp, and [Pt(3)(mu(3)-S)(2)(dppp)(3)](PF(6))(2). The first protonation step of the [Pt(2)S(2)] core leads to the stable [Pt(2)(mu-S)(mu-SH)(P intersection P)(2)](+) complex, but the second step implies disintegration of the ring, thus giving rise to various mononuclear species. The subsequent evolution of some of these species allows regeneration of [Pt(2)(mu-S)(mu-SH)(P intersection P)(2)](+), evidencing the cyclic nature of this process. Whereas the reaction pathway is essentially common for both phosphine ligands, dppe and dppp, the different coordinating ability of Cl(-) or ClO(4) (-) determines the nature of the final products, [PtCl(2)(P intersection P)], [Pt(3)(mu(3)-S)(2)(P intersection P)(3)]Cl(2) or [Pt(3)(mu(3)-S)(2)(P intersection P)(3)](ClO(4))(2). DFT calculations have corroborated the thermodynamic feasibility of the reactions proposed on the basis of experimental data.     

Study on platinum(II) induced formation of dithiiranes

The reaction of a series of stable alpha-chlorinated oligosulfanes 2 and 3 with [Pt(eta(2)-C(2)H(4))(Ph(3)P)2] 1 have been investigated. Starting with the alpha-chlorodisulfanes 2 a,b, the platinum dichloride complex 5 and the side-on bonded thioketone platinum complexes 6 a,b were formed. Complex 1 was treated with corresponding trisulfanes 3 a,b to give 5, 6 a,b and the dithiolatocomplexes 7 a,b. We assume that the {Pt(0)(Ph(3)P)2}-complex fragment inserted along the S--S bond to form the unstable intermediate G, which decomposed to form the products described above. We could prove that the sterically crowded 1,2,4-trithiolane 8 was not involved in the reaction pathway by treatment of 1 with 8 under the same conditions; after 24 h, 8 was found to be unreacted. X-ray structure analyses were performed on complexes 6 a, 7 a and 7 b.     

Structural and spectral studies of a new copper(II) complex with a tridentate thiosemicarbazone ligand

The reaction of copper(II) chloride dihydrate with 2-hydroxy-3-methoxybenzaldehydethiosemicarbazone (HL) ligand in a 1:1 ratio forms the complex [Cu(L)(Cl)] · H₂O. The complex is characterized by spectroscopic, electrochemical, and thermal analysis. X-ray crystallographic analysis reveals that the central copper atom displays the distorted square planar geometry. The water molecule present in the lattice participates in a strong hydrogen bonding network, which leads to a 2D supramolecular arrangement.     

Photophysical Study on the Rigid Pt(II) Complex [Pt(naphen)(Cl)] (Hnaphen = Naphtho[1,2-b][1,10]Phenanthroline and Derivatives

The electrochemistry and photophysics of the Pt(II) complexes [Pt(naphen)(X)] (Hnaphen = naphtho[1,2-b][1,10]phenanthroline, X = Cl or C≡CPh) containing the rigid tridentate C^N^N-coordinating pericyclic naphen ligand was studied alongside the complexes of the tetrahydro-derivative [Pt(thnaphen)(X)] (Hthnaphen = 5,6,8,9-tetrahydro-naphtho[1,2-b][1,10]phenanthroline) and the N^C^N-coordinated complex [Pt(bdq)(Cl)] (Hbdq = benzo[1,2-h:5,4-h’]diquinoline. The cyclic voltammetry showed reversible reductions for the C^N^N complexes, with markedly fewer negative potentials (around −1.6 V vs. ferrocene) for the complexes containing the naphen ligand compared with the thnaphen derivatives (around −1.9 V). With irreversible oxidations at around +0.3 V for all of the complexes, the naphen made a difference in the electrochemical gap of about 0.3 eV (1.9 vs. 2.2 eV) compared with thnaphen. The bdq complex was completely different, with an irreversible reduction at around −2 V caused by the N^C^N coordination pattern, which lacked a good electron acceptor such as the phenanthroline unit in the C^N^N ligand naphen. Long-wavelength UV-Vis absorption bands were found around 520 to 530 nm for the C^N^N complexes with the C≡CPh coligand and were red-shifted when compared with the Cl derivatives. The N^C^N-coordinated bdq complex was markedly blue-shifted (493 nm). The steady-state photoluminescence spectra showed poorly structured emission bands peaking at around 630 nm for the two naphen complexes and 570 nm for the thnaphen derivatives. The bdq complex showed a pronounced vibrational structure and an emission maximum at 586 nm. Assuming mixed ³LC/³MLCT excited states, the vibronic progression for the N^C^N bdq complex indicated a higher LC character than assumed for the C^N^N-coordinated naphen and thnaphen complexes. The blue-shift was a result of the different N^C^N vs. C^N^N coordination. The photoluminescence lifetimes and quantum yields Φ_L massively increased from solutions at 298 K (0.06 to 0.24) to glassy frozen matrices at 77 K (0.80 to 0.95). The nanosecond time-resolved study on [Pt(naphen)(Cl)] showed a phosphorescence emission signal originating from the mixed ³LC/³MLCT with an emission lifetime of around 3 µs.     

High thermodynamic stability and extraordinary kinetic inertness of copper(II) complexes with 1,4,8,11-tetraazacyclotetradecane-1,8-bis(methylphosphonic acid): example of a rare isomerism between kinetically inert penta- and hexacoordinated copper(II) complexes

In an aqueous solution at room temperature, 1,4,8,11-tetraazacyclotetradecane-1,8-bis(methylphosphonic acid) (H(4)L(1)) and Cu(I) (I) form a pentacoordinated (pc) complex, pc-[Cu(L(1))](2-), exhibiting conformation I of the cyclam ring. At high temperature, the complex isomerises to a hexacoordinated isomer, trans-O,O-[Cu(L(1))](2-), with a trans-III conformation of the cyclam ring. In pc-[Cu(L(1))](2-), four ring nitrogen atoms and one phosphonate oxygen atom are arranged around Cu(I) (I) in a structure that is half-way between a trigonal bipyramid and a tetragonal pyramid, with one phosphonic acid group uncoordinated. In the trans-O,O-[Cu(L(1))](2-) isomer, the nitrogen atoms form a plane and the phosphonic acid groups are in a mutually trans configuration. A structurally very similar ligand, 4-methyl-1,4,8,11-tetraazacyclotetradecane-1,8-bis(methylphosphonic acid) (H(4)L(2)), forms an analogous pentacoordinated complex, pc-[Cu(L(2))](2-), at room temperature. However, the complex does not isomerise to the octahedral complex analogous to trans-O,O-[Cu(L(1))](2-). Because of the high thermodynamic stability of pc-[Cu(L(1))](2-), (logbeta=25.40(4), 25 degrees C, I=0.1 mol dm(-3) KNO(3)) and the formation of protonated species, Cu(I) (I) is fully complexed in acidic solution (-log [H(+)] approximately 3). Acid-assisted decomplexation of both of the isomers of [Cu(H(2)L(1))] takes place only after protonation of both uncoordinated oxygen atoms of each phosphonate moiety and at least one nitrogen atom of the cycle. The exceptional kinetic inertness of both isomers is illustrated by their half-lives tau(1/2)=19.7 min for pc-[Cu(H(2)L(1))] and tau(1/2) about seven months for trans-O,O-[Cu(H(2)L(1))] for decomplexation in 5 M HClO(4) at 25 degrees C. The mechanism of formation of pc-[Cu(L(1))](2-) is similar to those observed for other macrocyclic complexes.     

2,4-二硝基酚与二氟溴甲基膦酸二乙酯反应的研究

酚在碱性条件下与卤代烃反应生成相应的芳香醚,是典型的亲核取代反应,对于2,4-二硝基酚和二氟溴甲基膦酸二乙酯在碱性条件下的反应,其实验过程包括室温中和,甲苯回流脱水和亲核取代等三步反应。对产物进行了提纯和一系列的表征,结果发现主要生成了一种酚醚化合物。     

Diverse structures and magnetism of cobalt(II) and manganese(II) compounds with mixed azido and carboxylato bridges induced by methylpyridinium carboxylates

Herein we present a systematic study of the structures and magnetic properties of six coordination compounds with mixed azide and zwitterionic carboxylate ligands, [M(N₃)₂(2‐mpc)] (2‐mpc=N‐methylpyridinium‐2‐carboxylate; M=Co for 1 and Mn for 2 ), [M(N₃)₂(4‐mpc)] (4‐mpc=N‐methylpyridinium‐4‐carboxylate; M=Co for 3 and Mn for 4 ), [Co₃(N₃)₆(3‐mpc)₂(CH₃OH)₂] ( 5 ), and [Mn₃(N₃)₆(3‐mpc)₂] ( 6 ; 3‐mpc=N‐methylpyridinium‐3‐carboxylate). Compounds 1 – 3 consist of one‐dimensional uniform chains with (μ‐EO‐N₃)₂(μ‐COO) triple bridges (EO=end‐on); 5 is also a chain compound but with alternating [(μ‐EO‐N₃)₂(μ‐COO)] triple and [(EO‐N₃)₂] double bridges; Compound 4 contains two‐dimensional layers with alternating [(μ‐EO‐N₃)₂(μ‐COO)] triple, [(μ‐EO‐N₃)(μ‐COO)] double, and (EE‐N₃) single bridges (EE=end‐to‐end); 6 is a layer compound in which chains similar to those in 5 are cross‐linked by a μ₃‐1,1,3‐N₃ azido group. Magnetically, the three Co^II compounds ( 1 , 3 , and 5 ) all exhibit intrachain ferromagnetic interactions but show distinct bulk properties: 1 displays relaxation dynamics at very low temperature, 3 is an antiferromagnet with field‐induced metamagnetism due to weak antiferromagnetic interchain interactions, and 5 behaves as a noninnocent single‐chain magnet influenced by weak antiferromagnetic interchain interactions. The magnetic differences can be related to the interchain interactions through π–π stacking influenced by different substitution positions in the ligands and/or different magnitudes of intrachain coupling. All of the Mn^II compounds show overall intrachain/intralayer antiferromagnetic interactions. Compound 2 shows the usual one‐dimensional antiferromagnetism, whereas 4 and 6 exhibit different weak ferromagnetism due to spin canting below 13.8 and 4.6 K, respectively.     

Self-assembly of a tridentate Schiff-base ligand with Zn(II) in the presence of lanthanides: Novel crystal structures and spectroscopic properties

Condensation of picolinaldehyde with methyl 4-amino-3-hydroxy-benzoate resulted in the acquisition of a tridentate Schiff-base ligand (HL) which contains a structural moiety typical of octahedrally cored grid-type analogs. Reactions of HL with Zn(NO₃)₂ in the presence of Ln(NO₃)₃ [Ln = Sm(III), Tb(III) and Yb(III)] result in two types of complexes, viz. [Zn(HL)(L)]₂[Ln(NO₃)₅] [Sm(III), 1a and Tb(III), 1b] and [Zn(HL)L]₂[Yb(NO₃)₅]·C₃H₆O (1c). Despite applying two different synthetic protocols, the transition metal ion displayed a greater propensity towards the meridional tridentate pocket, which is reflected by XRD analysis, the ESI-MS technique and further supported by elemental analysis and IR characterization of each compound. In addition, we have compared the luminescence properties of 1a, 1b and 1c with the previously synthesized [Zn(HL)(L)]₂[Zn(NO₃)₄] (1d) to investigate whether a different metal in the outer coordination sphere could somehow tune the compounds’ spectral behavior.     

Interaction of methyltin(IV) compounds with carboxylate ligands. Part 1: formation and stability of methyltin(IV)–carboxylate complexes and their relevance in speciation studies of natural waters

Quantitative data on the stability of mono‐, di‐ and trimethyltin(IV)‐carboxylate complexes (acetate, malonate, succinate, malate, oxydiacetate, diethylenetrioxydiacetate, tricarballylate, citrate, butanetetracarboxylate and mellitate) are reported at t = 25 °C and I→ 0 mol l^?1. Several mononuclear, mixed proton, mixed hydroxo and polynuclear species are formed in these systems. As expected, the stability trend is mono‐ > di‐ > trimethyltin(IV) and mono < di < tri < tetra < hexa for the organotin moieties and carboxylate ligands investigated, respectively. Moreover, ligands containing, in addition to carboxylic,? O? and? OH groups show a significantly higher stability with respect to analogous ligands with the same number of carboxylic binding sites. The results obtained from all the systems investigated allowed us to formulate the following empirical predictive equation for correlation between complex stability and some simple structural parameters, (1) where n_carb and n_OH are the number of carboxylic and alcoholic groups in the ligand, respectively, r is the stoichiometric coefficient of H⁺ (positive) or OH^? (negative) and z_cat is the methyltin cation charge (CH₃)_xSn^z+ (z⁺ = 4 ? x). Distribution diagrams for some representative systems are also reported and are discussed in the light of speciation studies in natural waters. A literature data comparison is made with carboxylate complexes of other metal ions with the same charge as the organotin cations investigated here. Copyright © 2005 John Wiley & Sons, Ltd.     

Carbon‐iodide bond activation by cyclometalated Pt (II) complexes bearing tricyclohexylphosphine ligand: A comparative kinetic study and theoretical elucidation

Cyclometalated Pt (II) complexes [PtMe(C^N)(L)], in which C^N = deprotonated 2,2′‐bipyridine N‐oxide (Obpy), 1 , deprotonated 2‐phenylpyridine (ppy), 2 , deprotonated benzo [h] quinolone (bzq), 3 , and L = tricyclohexylphosphine (PCy₃) were prepared and fully characterized. By treatment of 1–3 with excess MeI, the thermodynamically favored Pt (IV) complexes cis‐[PtMe₂I(C^N)(PCy₃)] (C^N = Obpy, 1a ; ppy, 2a ; and bzq, 3a ) were obtained as the major products in which the incoming methyl and iodine groups adopted cis positions relative to each other. All the complexes were characterized by means of NMR spectroscopy while the absolute configuration of 1a was further determined by X‐ray crystal structure analysis. The reaction of methyl iodide with 1–3 were kinetically explored using UV–vis spectroscopy. On the basis of the kinetic data together with the time‐resolved NMR investigation, it was established that the oxidative addition reaction occurred through the classical S_N2 attack of Pt (II) center on the MeI reagent. Moreover, comparative kinetic studies demonstrated that the electronic and steric nature of either the cyclometalating ligands or the phosphine ligand influence the rate of reaction. Surprisingly, by extending the oxidative addition reaction time, very stable iodine‐bridged Pt (IV)‐Pt (IV) complexes [Pt₂Me₄(C^N)₂(μ‐I)₂] (C^N = Obpy, 1b ; ppy, 2b ; and bzq, 3b ) were obtained and isolated. In order to find a reasonable explanation for the observation, a DFT (density functional theory) computational analysis was undertaken and it was found that the results were consistent with the experimental findings.     

Synthesis and structure of V(V) and Mn(III) NHC complexes supported by a tridentate bis-aryloxide-N-heterocyclic carbene ligand

Vanadium (V) and manganese (III) metal complexes (2, [^tBu(OCO)]V(O)Cl; 3, [^tBu(OCO)]Mn(acac)), which are supported by a tridentate bis-aryloxide-N-heterocyclic carbene ligand ([^tBu(OCO)]²⁻[η³-O,C,O-{(3,5-di-tert-butyl-C₆H₂O)₂N₂C₃H₄}]²⁻) have been prepared and structurally characterized. Both complexes were efficiently synthesized in a straightforward and smooth manner involving the direct reaction of the imidazolinium proligand 1,3-bis(3,5-di-tert-butyl-2-hydroxyphenyl)imidazolinium chloride 1, easily accessible in a two-step synthesis with an overall good yield, with (ⁱPrO)₃VO and Mn(acac)₃, respectively.     

Cyclometallated Pt(II) and Pd(II) complexes with a trithiacrown ligand

We report the synthesis and full characterization for a series of cyclometallated complexes of Pt(II) and Pd(II) incorporating the fluxional trithiacrown ligand 1,4,7-trithiacyclononane ([9]aneS3). Reaction of [M(C insertion mark N)(micro-Cl)]2 (M = Pt(II), Pd(II); C insertion mark N = 2-phenylpyridinate (ppy) or 7,8-benzoquinolinate (bzq)) with [9]aneS3 followed by metathesis with NH4PF6 yields [M(C insertion mark N)([9]aneS3)](PF6). The complexes [M(C insertion mark P)([9]aneS3)](PF6) (M = Pt(II), Pd(II); Cinsertion markP = [CH2C6H4P(o-tolyl)2-C,P]-) were synthesized from their respective [Pt(C insertion mark P)(micro-Cl)]2 or [Pd(C insertion mark P)(micro-O2CCH3)]2 (C insertion mark P) starting materials. All five new complexes have been fully characterized by multinuclear NMR, IR and UV-Vis spectroscopies in addition to elemental analysis, cyclic voltammetry, and single-crystal structural determinations. As expected, the coordinated [9]aneS3 ligand shows fluxional behavior in its NMR spectra, resulting in a single 13C NMR resonance despite the asymmetric coordination environment of the cyclometallating ligand. Electrochemical studies reveal irreversible one-electron metal-centered oxidations for all Pt(II) complexes, but unusual two-electron reversible oxidations for the Pd(II) complexes of ppy and bzq. The X-ray crystal structures of each complex indicate an axial M-S interaction formed by the endodentate conformation of the [9]aneS3 ligand. The structure of [Pd(bzq)([9]aneS3)](PF6) exhibits disorder in the [9]aneS3 conformation indicating a rare exodentate conformation as the major contributor in the solid-state structure. DFT calculations on [Pt([9]aneS3)(ppy)](PF6) and [Pd([9]aneS3)(ppy)](PF6) indicate the HOMO for both complexes is primarily dz2 in character with a significant contribution from the phenyl ring of the ppy ligand and p orbital of the axial sulfur donor. In contrast, the calculated LUMO is primarily ppy pi* in character for [Pt([9]aneS3)(ppy)](PF6), but dx2-y2 in character for [Pd([9]aneS3)(ppy)](PF6).     

A Heteroleptic Push–Pull Substituted Iron(II) Bis(tridentate) Complex with Low‐Energy Charge‐Transfer States

A heteroleptic iron(II) complex [Fe(dcpp)(ddpd)]²⁺ with a strongly electron‐withdrawing ligand (dcpp, 2,6‐bis(2‐carboxypyridyl)pyridine) and a strongly electron‐donating tridentate tripyridine ligand (ddpd, N,N′‐dimethyl‐N,N′‐dipyridine‐2‐yl‐pyridine‐2,6‐diamine) is reported. Both ligands form six‐membered chelate rings with the iron center, inducing a strong ligand field. This results in a high‐energy, high‐spin state (⁵T₂, (t_2g)⁴(e_g*)²) and a low‐spin ground state (¹A₁, (t_2g)⁶(e_g*)⁰). The intermediate triplet spin state (³T₁, (t_2g)⁵(e_g*)¹) is suggested to be between these states on the basis of the rapid dynamics after photoexcitation. The low‐energy π^* orbitals of dcpp allow low‐energy MLCT absorption plus additional low‐energy LL′CT absorptions from ddpd to dcpp. The directional charge‐transfer character is probed by electrochemical and optical analyses, Mößbauer spectroscopy, and EPR spectroscopy of the adjacent redox states [Fe(dcpp)(ddpd)]³⁺ and [Fe(dcpp)(ddpd)]⁺, augmented by density functional calculations. The combined effect of push–pull substitution and the strong ligand field paves the way for long‐lived charge‐transfer states in iron(II) complexes.     

Design and synthesis of a Pt(II) nanoscopic trigonal bipyramidal cage using a new tripodal ester-containing ligand

The formation of a Pt(II) nanoscopic trigonal bipyramidal cage (TBP) containing a new tripodal linker with ester functionality is achieved by self-assembly. The new tripod ligand and the cage were characterized by multinuclear NMR and electrospray ionization mass spectroscopy. Energy minimized simulation of the cage yielded a pseudo TBP shape with an internal diameter of 2 nm.