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1.
Nat Commun ; 15(1): 5024, 2024 Jun 12.
Artículo en Inglés | MEDLINE | ID: mdl-38866773

RESUMEN

Chemical etching of nano-sized metal clusters at the atomic level has a high potential for creating metal number-specific structures and functions that are difficult to achieve with bottom-up synthesis methods. In particular, precisely etching metal atoms one by one from nonmetallic element-centred metal clusters and elucidating the relationship between their well-defined structures, and chemical and physical properties will facilitate future materials design for metal clusters. Here we report the single-gold etching at a hypercarbon centre in gold(I) clusters. Specifically, C-centred hexagold(I) clusters protected by chiral N-heterocyclic carbenes are etched with bisphosphine to yield C-centred pentagold(I) (CAuI5) clusters. The CAuI5 clusters exhibit an unusually large bathochromic shift in luminescence, which is reproduced theoretically. The etching mechanism is experimentally and theoretically suggested to be a tandem dissociation-association-elimination pathway. Furthermore, the vacant site of the central carbon of the CAuI5 cluster can accommodate AuCl, allowing for post-functionalisation of the C-centred gold(I) clusters.

2.
ACS Org Inorg Au ; 3(6): 371-376, 2023 Dec 06.
Artículo en Inglés | MEDLINE | ID: mdl-38075454

RESUMEN

Although stereochemical control of carbon centers is a well-established technique in modern synthetic chemistry, that of tetrahedral metal complexes with a stereogenic metal center remains difficult due to the dynamic nature of their coordination bonds. Here we report the synthesis of a tetrahedral d8 high-spin chiral-at-nickel(II) complex composed exclusively of achiral ligands and the supramolecular control of its temperature-dependent spontaneous resolution in crystals. Under certain conditions, complex molecules with the same absolute configuration of the nickel(II) center grow into conglomerate crystals with a helically arranged structure due to intermolecular hydrogen bonding. This process is highly spontaneous, does not require any chiral sources, and is closely related to the origin of homochirality in biological systems. The obtained enantiopure nickel(II) complex will be a new type of redox-active chiral source for asymmetric synthetic chemistry.

3.
Chem Sci ; 14(23): 6207-6215, 2023 Jun 14.
Artículo en Inglés | MEDLINE | ID: mdl-37325149

RESUMEN

The properties of metal clusters are highly dependent on their molecular surface structure. The aim of this study is to precisely metallize and rationally control the photoluminescence properties of a carbon(C)-centered hexagold(i) cluster (CAuI6) using N-heterocyclic carbene (NHC) ligands with one pyridyl, or one or two picolyl pendants and a specific number of silver(i) ions at the cluster surface. The results suggest that the photoluminescence of the clusters depends highly on both the rigidity and coverage of the surface structure. In other words, the loss of structural rigidity significantly reduces the quantum yield (QY). The QY in CH2Cl2 is 0.04 for [(C)(AuI-BIPc)6AgI3(CH3CN)3](BF4)5 (BIPc = N-isopropyl-N'-2-picolylbenzimidazolylidene), a significant decrease from 0.86 for [(C)(AuI-BIPy)6AgI2](BF4)4 (BIPy = N-isopropyl-N'-2-pyridylbenzimidazolylidene). This is due to the lower structural rigidity of the ligand BIPc because it contains a methylene linker. Increasing the number of capping AgI ions, i.e., the coverage of the surface structure, increases the phosphorescence efficiency. The QY for [(C)(AuI-BIPc2)6AgI4(CH3CN)2](BF4)6 (BIPc2 = N,N'-di(2-pyridyl)benzimidazolylidene) recovers to 0.40, 10-times that of the cluster with BIPc. Further theoretical calculations confirm the roles of AgI and NHC in the electronic structures. This study reveals the atomic-level surface structure-property relationships of heterometallic clusters.

4.
Dalton Trans ; 52(11): 3295-3299, 2023 Mar 14.
Artículo en Inglés | MEDLINE | ID: mdl-36648316

RESUMEN

Mononuclear oxovanadium(V) complexes [V(O)XL (1: X = Ot-Bu, 2: X = Cl)] [H2L: 2,2'-methylene bis(4,6-di-tert-butylphenol)(4'-tert-butyl-6'-(1-adamantyl)phenol)] directed towards asymmetric catalysis have been synthesised as racemic compounds using an unsymmetric and achiral phenolic bidentate ligand (H2L), and NMR and UV-vis absorption spectroscopies, single-crystal X-ray diffraction, and IR spectroscopy revealed their racemic chiral-at-vanadium structures in solution and in the crystal. In addition, theoretical calculations revealed that the HOMO-LUMO energy gap is smaller for unsymmetric ligands, which promotes d-orbital splitting of the metal centre.

5.
Nat Commun ; 13(1): 4288, 2022 08 10.
Artículo en Inglés | MEDLINE | ID: mdl-35948553

RESUMEN

Photoluminescent gold clusters are functionally variable chemical modules by ligand design. Chemical modification of protective ligands and introduction of different metals into the gold clusters lead to discover unique chemical and physical properties based on their significantly perturbed electronic structures. Here we report the synthesis of carbon-centered Au(I)-Ag(I) clusters with high phosphorescence quantum yields using N-heterocyclic carbene ligands. Specifically, a heterometallic cluster [(C)(AuI-L)6AgI2]4+, where L denotes benzimidazolylidene-based carbene ligands featuring N-pyridyl substituents, shows a significantly high phosphorescence quantum yield (Φ = 0.88). Theoretical calculations suggest that the carbene ligands accelerate the radiative decay by affecting the spin-orbit coupling, and the benzimidazolylidene ligands further suppress the non-radiative pathway. Furthermore, these clusters with carbene ligands are taken up into cells, emit phosphorescence and translocate to a particular organelle. Such well-defined, highly phosphorescent C-centered Au(I)-Ag(I) clusters will enable ligand-specific, organelle-selective phosphorescence imaging and dynamic analysis of molecular distribution and translocation pathways in cells.


Asunto(s)
Oro , Metano , Oro/química , Ligandos , Metano/análogos & derivados , Metano/química , Orgánulos
6.
J Am Chem Soc ; 144(5): 2156-2163, 2022 02 09.
Artículo en Inglés | MEDLINE | ID: mdl-35084822

RESUMEN

Asymmetric induction of metal clusters by ligation of chiral ligands is intriguing in terms of the mechanism of chirality transfer and the stability of the resulting chiral structure. Here we report the asymmetric induction of C-centered hexagold(I) CAuI6 clusters into an asymmetrically twisted structure through monodentate, chiral benzimidazolylidene-based N-heterocyclic carbene (NHC) ligands. X-ray diffraction analysis revealed that the NHC-ligated CAuI6 cluster was diastereoselectively twisted with directionally selective, bond length expansion, and contraction of the Au···Au contacts and that the original cluster with high symmetry was transformed into an optically pure, asymmetric CAuI6 cluster with C1 symmetry. Moreover, the circular dichroism spectroscopy and the time-dependent density functional theory calculation confirmed that the asymmetrically twisted CAuI6 structure was maintained even in solution. Such asymmetric induction of configurationally stable metal clusters would greatly expand the molecular design possibilities of asymmetric catalysts and chiroptical materials by utilizing library chiral NHC ligands.

7.
Nat Commun ; 11(1): 6263, 2020 12 09.
Artículo en Inglés | MEDLINE | ID: mdl-33298960

RESUMEN

Chiral metal complexes show promise as asymmetric catalysts and optical materials. Chiral-at-metal complexes composed of achiral ligands have expanded the versatility and applicability of chiral metal complexes, especially for octahedral and half-sandwich complexes. However, Werner-type tetrahedral complexes with a stereogenic metal centre are rarely used as chiral-at-metal complexes because they are too labile to ensure the absolute configuration of the metal centre. Here we report the asymmetric construction of a tetrahedral chiral-at-zinc complex with high configurational stability, using an unsymmetric tridentate ligand. Coordination/substitution of a chiral auxiliary ligand on zinc followed by crystallisation yields an enantiopure chiral-only-at-zinc complex (> 99% ee). The enantiomer excess remains very high at 99% ee even after heating at 70 °C in benzene for one week. With this configurationally stable zinc complex of the tridentate ligand, the remaining one labile site on the zinc can be used for a highly selective asymmetric oxa-Diels-Alder reaction (98% yield, 87% ee) without substantial racemisation.

8.
J Am Chem Soc ; 142(1): 407-416, 2020 01 08.
Artículo en Inglés | MEDLINE | ID: mdl-31804816

RESUMEN

Self-assembled metal-organic architectures have great potential to undergo major structural changes into different architectures. Such molecular transformation is widely applicable to responsive systems like drug delivery and allosteric catalysis. A great number of metal-organic architectures responsive to a specific stimulus have been reported so far. However, interconversion between a pair of distinct metal-organic structures in response to multiple stimuli is rarely reported despite its high versatility. Herein we report multi-stimuli-responsive interconversion between a bowl-shaped and a capsule-shaped self-assembled ZnII complexes, [ZnII4L3X6] and [ZnII4L4], respectively, which were found to form in equilibrium from porphyrin-based ligand L and ZnII ions with different stoichiometry. Specifically, this interconversion was induced by four distinct external stimuli: exogenous ligands, Brønsted base/acid, solvents, and guest molecules. The mechanisms of the interconversion system are discussed in detail focusing on the species included in the equilibria. Thus, these findings would provide a helpful clue to design principles for multi-stimuli-responsive systems with functional versatility.

9.
J Am Chem Soc ; 141(26): 10384-10389, 2019 07 03.
Artículo en Inglés | MEDLINE | ID: mdl-31189315

RESUMEN

Hetero-multinuclear metal complexes are a promising class of compounds applicable to photoluminescence, magnetism, and catalysis. In this work, we have developed a synthetic method for hetero-tetranuclear metal complexes by combining advantages of site-selective redox switching and transmetalation. First, a homo-tetranuclear CoII4 complex was converted to a mixed-valence CoIIICoII3 complex by site-selective oxidation, which was then transmetalated from CoII to NiII to form a heterometallic CoIIINiII3 complex. Finally, a CoIINiII3 complex was synthesized by metal-selective reduction on the CoIII site. The basic structural frameworks of the main products in the whole process starting from the CoII4 complex are isostructural. Notably, the CoIINiII3 complex was not accessible by direct mixing of ligand, CoII, and NiII. This method would provide an alternative strategy for highly selective synthesis of hetero-multinuclear metal complexes.

10.
J Am Chem Soc ; 139(46): 16470-16473, 2017 11 22.
Artículo en Inglés | MEDLINE | ID: mdl-29061040

RESUMEN

Herein we report the synthesis of a circularly arranged sextuple triptycene gear molecule, hexakis(10-dodecyloxy-9-triptycyl)ethynylbenzene, via the trimerization of the corresponding triyne with a cobalt catalyst. The six triptycene gears are closely engaged with each other as confirmed by single crystal X-ray structure analysis, and their motion in solution was established by NMR spectroscopy. Notably, when one bulky RuCp* complex was attached to one triptycene gear, the whole movement of the six gears was highly restricted via their mechanical engagement. Development of such a multigear molecule would provide a structural basis for molecular motion transmission systems with a switching function.

11.
Nat Commun ; 8: 14296, 2017 02 08.
Artículo en Inglés | MEDLINE | ID: mdl-28176770

RESUMEN

Metal ions can serve as a centre of molecular motions due to their coordination geometry, reversible bonding nature and external stimuli responsiveness. Such essential features of metal ions have been utilized for metal-mediated molecular machines with the ability to motion switch via metallation/demetallation or coordination number variation at the metal centre; however, motion switching based on the change in coordination geometry remain largely unexplored. Herein, we report a PtII-centred molecular gear that demonstrates control of rotor engagement and disengagement based on photo- and thermally driven cis-trans isomerization at the PtII centre. This molecular rotary motion transmitter has been constructed from two coordinating azaphosphatriptycene rotators and one PtII ion as a stator. Isomerization between an engaged cis-form and a disengaged trans-form is reversibly driven by ultraviolet irradiation and heating. Such a photo- and thermally triggered motional interconversion between engaged/disengaged states on a metal ion would provide a selector switch for more complex interlocking systems.

12.
J Am Chem Soc ; 138(9): 2945-8, 2016 Mar 09.
Artículo en Inglés | MEDLINE | ID: mdl-26910765

RESUMEN

Self-assembled molecular machines have great potential to enable noncovalent regulation of a coupled motion of the building blocks. Herein we report the synthesis and the rotational control of a lantern-type dirhodium complex with circularly arranged four 2,3,6,7,14,15-hexamethyltriptycene carboxylates as gears and two axial ligands as the rate control elements. The rotating rates in solution were markedly affected by the coordination ability and the bulkiness of axial ligands. Notably, the rate changes were closely correlated with the changes in the electronic states of the dirhodium center. Such ligand exchange-based control of rotational motions with color changes would advance stimulus-responsive metallo-molecular multirotors.

13.
J Am Chem Soc ; 135(50): 18790-3, 2013 Dec 18.
Artículo en Inglés | MEDLINE | ID: mdl-24299460

RESUMEN

Coordination-driven self-assembly utilizing labile capping ligands has been exploited as a novel strategy for metallo-cage containers. Herein, we report a tetrameric porphyrin barrel complex [C60⊂Zn814(H2O)4(OTs)12](OTs)4 (2) (OTs = p-CH3C6H4SO3) formed from a tetrakis(bipyridyl)porphyrin ligand 1, Zn(OTs)2, and a template guest, C60 fullerene. The tetrameric-barrel 2 contains two kinds of bis(bpy) Zn(II) centers coordinated by TsO(-) anions which serve as labile capping ligands in the formation of the finite structure of 2.

15.
Angew Chem Int Ed Engl ; 52(2): 720-3, 2013 Jan 07.
Artículo en Inglés | MEDLINE | ID: mdl-23161786

RESUMEN

Construction of a self-assembled cage complex through three different Zn(II) centers is achieved using a Zn porphyrin ligand with four 2,2'-bipyridin-5-yl (bpy) groups. The multiporphyrin cage encapsulates guest molecules unsymmetrically by π-π interactions. Well-balanced aqueous conditions, which allow the formation of both tris(bpy) and hydrated bis(bpy) Zn(II) units, result in the unsymmetrical yet well-defined supramolecular structure.

18.
Bioorg Med Chem Lett ; 19(14): 3895-8, 2009 Jul 15.
Artículo en Inglés | MEDLINE | ID: mdl-19375310

RESUMEN

The enantioselective activation of nitroalkanes was attempted on the basis of the complexation between chiral guanidinium and nitronate through two hydrogen bonds. The proposed enantioselective activation was applied to the diastereo- and enantioselective Henry (nitroaldol) reaction of nitroalkanes with aldehydes using axially chiral guanidine bases as the catalyst. Optically active nitroaldol products were obtained in acceptable yields with fairly good enantio- and diastereoselectivities at low temperature.


Asunto(s)
Guanidina/química , Nitrocompuestos/química , Aldehídos/química , Catálisis , Enlace de Hidrógeno , Nitrocompuestos/síntesis química , Estereoisomerismo , Temperatura
20.
J Am Chem Soc ; 128(50): 16044-5, 2006 Dec 20.
Artículo en Inglés | MEDLINE | ID: mdl-17165751

RESUMEN

A newly designed axially chiral guanidine is found to function as an effective platform for asymmetric induction at the alpha-carbon of unsymmetrically substituted 1,3-dicarbonyl compounds. Highly efficient and enantioselective electrophilic amination of various 1,3-dicarbonyl compounds with azodicarboxylate was successfully achieved using the present chiral guanidine catalyst, which provides efficient access to the construction of nitrogen-substituted quaternary stereocenters in an optically active form.


Asunto(s)
Electrones , Guanidina/química , Aminación , Catálisis , Estructura Molecular , Estereoisomerismo
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