A neutral octa-nuclear AuI-cluster (2) with molecular formula [(Cy-cAACPAu)4(AuCl)4] [Cy-cAAC =:C(N-2,6-iPr2C6H3)(C6H10)(CMe2)(CH2)] has been isolated, and structurally characterized by single-crystal X-ray diffraction. 2 has been further studied by NMR and ESI-MS. The μ3-P bridged AuI-cluster 2 possesses a C2 axis that passes through the two Au atoms positioned oppositely of the central Au(I)4P4 core, and two carbene-P chromophores. The emission spectrum of 2 exhibited a broad band with λem at 720 nm, and an average lifetime of 3.36 ns when excited at 388 nm in solid state at room temperature. Cyclic voltammetry (CV) studies revealed that 2 can undergo reversible one-electron oxidation at 0.76 V. The electronic transition in 2 has been further studied by computational methods.

Six novel phosphine substituted [FeFe] hydrogenase models with phosphinate in the bridgehead were synthesized and investigated by FTIR spectroscopy and cyclic voltammetry (CV). These ligand exchange reactions occur at milder conditions compared to literature procedures, resulting in a ligand-specific main product in all cases. Additionally, reflux conditions only influenced the complexes with bidentate ligands.

Abstract

This work reports on ligand exchange reactions between a [FeFe] hydrogenase model containing the higher homologue (PhosDT) and phosphines selected to cover a variety of electronic properties and possible coordination modes. Additionally, the amount of the phosphines and the reaction temperature were varied to study the formation of complexes with multiple phosphines or altered binding modes. Due to steric effects caused by the position of the bridgehead, the phosphines bind preferentially at the more accessible iron centre on the phosphinate averted side. While all ligand exchanges resulted in a ligand-specific main product at room temperature, reflux conditions induced decomposition in case of PhosDT-(κ²-dppe) and PhosDT-(κ²-dppv) and a change in the binding mode for the dppm containing complex. Moreover, we highlight two novel iron complexes obtained as side products of the reactions with dppe and dppv, while in case of dppm an additional model with two bridging phosphine ligands was generated. Finally, the six novel phosphine substituted PhosDT models were electrochemically investigated, revealing a cathodic shift compared to the starting material due to the increased electron density at the iron atoms. Moreover, the models with monodentate ligands exhibit a different CV pattern for the Fe^IFe^I/Fe^IFe⁰ process than complexes with bidentate phosphines.

We report on the first peptoid-based catalyst for visible light driven water oxidation, the complex TPT2Co. Peptoids are N-substituted glycine oligomers, and TPT is a peptoid trimer incorporating terpyridine ligand, an ethanolic group as a proton acceptor and a non-catalytic benzyl group. We explored the ability of TPT2Co to perform as a catalyst for water oxidation in phosphate buffer at pH 9.5, in the presence of the photosensitizer [Ru(bpy)3]2+ and the sacrificial electron acceptor Na2S2O8. We demonstrated that TPT2Co can catalyze water oxidation by a blue LED with an intensity of only 1.5 mW/cm2 towards oxygen production at pH 9.5 with a maximal TON of 28.1 in 45 min. The stability of TPT2Co during the light-driven water oxidation as well as its ability to stabilize the photosensitizer were confirmed by a combination of UV-Vis, IR and ESI-MS analysis.

Abstract: The synthesis and characterization of Nickel(II) complexes with novel pincer-type N-heterocyclic carbene complexes were investigated. Nickel(II)-NHC complexes, 7 and 8, were characterized using HR ESI-MS, IR, UV-Visible, and elemental analysis. The complex 7 with less sterically demanding pincer ligand was investigated in the catalytic one pot synthesis of thioethers via coupling reactions of a series of aryl and alkyl halides in the presence of thiourea. In a mixture of water and ethanol, 5 mol% of 7 catalyzed the C-S bond coupling reaction in high yields.

To harness radiometals in clinical settings, a chelator forming a stable complex with the metal of interest and targets the desired pathological site is needed. Toward this goal, we previously reported a unique set of chelators that can stably bind to both large and small metal ions, via a conformational switch. Within this chelator class, py-macrodipa is particularly promising based on its ability to stably bind several medicinally valuable radiometals including large 132/135La3+, 213Bi3+, and small 44Sc3+. We report a 10-step organic synthesis of its bifunctional analogue py-macrodipa-NCS, which contains an amine-reactive –NCS group that is amenable for bioconjugation reactions to targeting vectors. The hydrolytic stability of py-macordipa-NCS was assessed, revealing a half-life of 6.0 d in pH 9.0 aqueous buffer. This bifunctional chelator was then conjugated to a prostate-specific membrane antigen (PSMA)-binding moiety, yielding the bioconjugate py-macrodipa-PSMA, which was subsequently radiolabeled with large 132/135La3+ and small 47Sc3+, revealing efficient and quantitative complex formation. The resulting radiocomplexes were injected into mice bearing both PSMA-expressing and PSMA-non-expressing tumor xenografts to determine their biodistribution patterns, revealing delivery of both 132/135La3+ and 47Sc3+ to PSMA+ tumor sites. Urine analysis, however, revealed partial radiometal dissociation, suggesting that py-macrodipa-PSMA needs further structural optimization.

An experimental study is presented involving biomimetic models of iron complexes, namely N4Py and its methyl-substituted analogs (^MeN4Py, N4Py^Me). These complexes were reacted with sodium chlorite at room temperature and physiological pH of 5.0. Our results demonstrate that the iron complexes efficiently oxidize chlorite via formation of iron(IV) oxo intermediates albeit via different reaction pathways.

Abstract

Chlorine oxyanions have various applications, such as bleaching and oxidizers in rocket fuels. However, their high solubility in water and long environmental lifetimes have led to ecological concerns, especially regarding drinking water quality. This study focuses on the conversion of chlorite to chlorine dioxide, which is of significant interest as it exhibits superior antimicrobial activity and generates less harmful byproducts for water treatment. Two nonheme iron(II) complexes capable of producing chlorine dioxide from chlorite at room temperature and pH 5.0 are presented. These complexes oxidize chlorite through high-valent iron (IV)-oxo intermediates formed in-situ. The study establishes second-order rate constants for chlorite oxidation and investigates the effects and mechanisms involved by substituting a methyl group in the secondary coordination sphere of the Fe^IV(O)(N4Py) system. By employing kinetic analysis and spectroscopic investigations, the crucial elements for the reaction mechanism in chlorite oxidation are identified. These findings pave the way for future advancements in this field.

Variations of the coordination of nortricyclane-type 7-atom polypnictides to metal ions were achieved upon reactions of either K₃As₇ with PbI₂ in ethane-1,2-diamine and subsequent layering with toluene or by reacting an extraction solution of ‘K₅Ga₂Bi₄’ in pyridine with [ZnPh₂] prior to layering with toluene. The two procedures were specific for the respective elemental combinations, and they afforded the second compound exhibiting the rare Bi₇ ³⁻ ion in the coordination sphere of transition metal ions.

Abstract

The formation and follow-up chemistry of P₇ ³⁻ has been intensely studied in the recent decades. In contrast, corresponding investigations of its heavier polycyclic polypnictide congeners Pn₇ ³⁻ (Pn=As, Sb, Bi), especially Bi₇ ³⁻, have been done to a much lesser extent. In our report, we add to these rare studies, by reporting new coordination compounds with As₇ ³⁻ and Bi₇ ³⁻, respectively. Addition of PbI₂ to a solution of K₃As₇ in ethane-1,2-diamine (en) afforded the heterometallic cluster anion [(As₇)Pb(As₇)]⁴⁻ (with an 8 % co-crystallization of [PbAs₁₅]³⁻ on the same site), in compound [K_3.92(crypt-222)₄][(As₇)Pb(As₇)]_0.92[PbAs₁₅]_0.08 ⋅ 3en (1). A similar reaction of [ZnPh₂] with a pyridine (py) solution of the ternary solid ‘K₅Ga₂Bi₄’, which was previously shown to release Ga and polybismuthide units in situ under certain reaction conditions, resulted in the formation of [K(crypt-222)]₄[(Bi₇)Zn(Bi₇)] ⋅ 2.5py (2), comprising the related heterometallic anion [(Bi₇)Zn(Bi₇)]⁴⁻. The former represents the first Pb−As binary Zintl anions obtained via solution chemistry, and the latter adds one more piece to the remarkably rare coordination compounds reported for Bi₇ ³⁻.

In this comparative study, two different nine-coordinated Eu³⁺ compounds with [DPA]²⁻ were crystallised. [Eu(DPA)(HDPA)(H₂O)₂] ⋅ 4H₂O and Na₃[Eu(DPA)₃] ⋅ 14H₂O were found to form in all samples, and the ratio between them can be controlled by pH. Despite the presence of both compounds in all samples, this was not evident from luminescence and PXRD data, althhough the data did not show the single crystal data properties.

Abstract

Two compounds, Na₃[Eu(DPA)₃] ⋅ 14H₂O and [Eu(DPA)(HDPA)(H₂O)₂] ⋅ 4H₂O, were created and the structure determined using single crystal X-ray diffraction. The single crystal luminescence properties were compared and related to the Eu³⁺ coordination geometry. The formation of single crystals from solutions of Eu(CF₃SO₃)₃ and H₂DPA was found change with the pH value of the H₂DPA solution. Mixtures of Na₃[Eu(DPA)₃] ⋅ 14H₂O and [Eu(DPA)(HDPA)(H₂O)₂] ⋅ 4H₂O were observed with a pH ratio between the two structures. While visual inspection showed that all samples contained both Na₃[Eu(DPA)₃] ⋅ 14H₂O and [Eu(DPA)(HDPA)(H₂O)₂] ⋅ 4H₂O, the PXRD and luminescence data did not immediately reveal that the samples were pure. Having discovered that the samples were indeed mixtures, quantification was attempted by Rietveld refinement of the PXRD data, and the luminescence spectra were compared to those from single crystals. As the data was not found to reveal that the samples were mixtures, even though we knew that this was the case, we must urge caution when inferring structure-property relationships from powder samples. In this case we were able to isolate monophasic systems and do a comparative study, but this requires that the samples are identified as mixtures.

Which is preferred, C-amino-(σ²,λ³)-phosphaalkene P=C or C-(σ³,λ³)-phosphinoimine N=C? The answer seems to depend on the backbone substituent R. When R is an aryl group (or hydrogen) P=C is consistently preferred over N=C, though both isomers exist in solution. When R is a ^t Bu or amino group, N=C is preferred, with no evidence for the other isomers in solution.

Abstract

This paper presents definitive structural evidence for N,P(III)-monophosphaamidines in P=C and N=C isomeric forms from a combination of new syntheses, single-crystal X-ray diffraction (SC-XRD), solid-state NMR and FTIR. Evidence is also provided for C-amino-(σ²,λ³)-phosphaalkene and C-(σ³,λ³)-phosphinoimine tautomerism in solution using multi-nuclear NMR methods. Synthesis and SC-XRD structure determination of a trisubstituted N,N’,P(III)-monophosphaguanidine is presented, the first structure of a phospha(III)guanidine with two ionizable H atoms. The structural evidence is convincing for an N=C geometry, resulting in both N−H and P−H in the molecule. A detailed computational investigation using DFT methods is presented, with the goal of understanding the tautomeric structure preferences both at the fundamental level (parent molecules with all substituents on the heteroatoms being hydrogen) and using the full structures containing the very bulky 2,6-diisopropylphenyl (Dipp) substituents employed in this study. Arguments are espoused for treating phospha(III)amidines and -guanidines as new types of functional groups, similar to but distinct from the familiar organic analogues. Limited reactivity studies and a voltammetry study of one phospha(III)amidine are included with the supporting information.

Analogous Pt^IV and Ir^III complexes containing α-diimines as N^N ligands exhibit distinctly different photophysical behavior. This arises from the metal-induced differences in the energy gaps between the excited ligand-centered ^3*LC and metal-to-ligand ^3*MLCT or ligand-to-metal ^3*LMCT charge transfer states.

Abstract

The paper deals with the synthesis of a series of cationic [Pt(ppz)₂(N^N)]²⁺ complexes containing deprotonated 1-phenyl-1H-pyrazole as cyclometallating (C^N) ligands and α-diimines (N^N) in the form of water-soluble salts with OTf⁻ (trifluoromethanesulfonate) counter ions. These complexes were obtained from cis-[Pt(ppz)₂Cl₂] through chloride ligands substitution with α-diimines. The complexes were identified by means of NMR spectroscopy and their molecular structures were confirmed by X-ray crystallography. The photophysical properties of these complexes were studied in detail. These complexes showed strong luminescence in MeOH/EtOH 1 : 1 glasses at 77 K but were almost non-emitting in MeCN solutions at room temperature. Their emission properties were compared to analogues Ir^III complexes.