Bottom-up construction of chiral metal-peptide assemblies from metal cluster motifs

Unlocking a Biological Interface of Chiral Supramolecular Helical Polymers

Here we report a C3-symmetric metal-binding tripeptide, BTMA-1, that self-assembles in water into either a chiral supramolecular helical polymer or a discrete CoII peptide helicate, depending on metal coordination. The CoII peptide helicate exhibits high affinity and selectivity toward DNA three-way junctions (3WJ), a class of noncanonical DNA structures with emerging biological relevance. Importantly, we demonstrate that the recognition process can be triggered dynamically by adding CoII ions to a dispersion of the supramolecular polymer, which acts as an inert precursor reservoir in physiological media. In this way, our strategy shows that chiral supramolecular helical polymers can form temporarily inactive aggregates that release discrete helicates for biomolecular recognition, such as 3WJ binding, upon metal ion coordination. Overall, this mechanism reveals a previously unexplored capability of this class of materials and offers a new approach for the design of responsive supramolecular systems for nucleic acid recognition and anticancer therapy.

Controlling the Chirality of Metallo-Cages by Manipulating the Stereochemistry of the Metal Centers

Precise control over the chirality of metallo-cages by manipulating the stereochemistry of metal centers is important in many practical applications, but is extremely challenging. In this study, two isostructural metallo-cuboctahedra (1-ZnII 12L18 and 2-CdII 12L18) have been assembled using ligand L1 and two kinds of metal ions (ZnII and CdII) with similar coordination lability. The chiral-induction by the same guests (D-/L-camphorsulfonate, D-/L-SCS) results in a completely opposing stereochemical output of 1 and 2: D-SCS induced host-guest complex of [D-SCS⊂Δ12-1] and [D-SCS⊂Λ12-2], respectively, with reverse handedness. The distinct stereochemical configuration of metallo-cuboctahedra can be manipulated by participant metal ions that exhibit similar dynamics. Furthermore, a subtle variation of the ligand peripheral substituent group facilitates spontaneous resolution of metallo-cuboctahedra 3-ZnII 12L28 from a racemic mixture as (R24, Λ12)-3/(S24, Δ12)-3 enantiopure entities. The dynamic stereochemistry of MII 12L8 cuboctahedra described in this work allows a chiral manipulation based on the nature of metal centers and ligands, enabling the design and control of the chirality of metallo-cages.

Singlet Carbenes Are Stereoinductive Main Group Ambiphiles

Stereogenic units are a critical source of molecular complexity, but their stereoselective formation via main group ambiphiles─which are suitable for derivatizing a wide scope of functionalities─is largely unexplored. Herein, using chiral cyclic (alkyl)(amino)carbenes (ChiCAACs), we study stereoinduction during the oxidative addition of E-H σ-bonds (E = C, N, O, Si, P). Through computational modeling, the relationship between stereochemical outcome and mechanism is elucidated, providing insight into when and why ChiCAACs exhibit excellent stereoselectivities. Altogether, these results demonstrate the potential for chiral main group ambiphiles to generate stereogenic units in a highly controlled manner opening avenues for applying "metal-like" reactivity in metal-free asymmetric syntheses.

Electrospray Ionization Mass Spectrometry Insights into the Assembly of Lanthanide-Containing Clusters

ConspectusAtomically precise metal clusters with well-defined crystal structures have emerged as a rapidly growing field within coordination and materials chemistry. Among them, lanthanide-containing clusters (LCCs) are particularly notable for their aesthetically pleasing architectures and intriguing properties. Achieving precise synthesis and accurate structural characterization of these clusters is crucial for unlocking their potential applications. Mass spectrometry (MS), particularly electrospray ionization mass spectrometry (ESI-MS), has proven to be a powerful tool, providing exceptional sensitivity and clarity in revealing the formation mechanisms and structural details of metal clusters. In this Account, we explore the synthesis, characterization, and assembly mechanisms of LCCs utilizing ESI-MS. We begin by tracing the historical development of LCCs, emphasizing the critical role of single-crystal X-ray diffraction in structural confirmation and the challenges associated with it. We then discuss the application of ESI-MS in characterizing LCCs, highlighting how this technique can monitor the formation processes of LCCs and determine their molecular weights and charge states. We introduce the mass difference fingerprint of isomorphism (MDFI) method, which can facilitate rapid analysis of LCCs' mass spectrometry data. Furthermore, we discuss the state of LCCs in solution and the challenges in their characterization. By utilizing ESI-MS, we enhance the understanding of the assembly mechanisms of LCCs and propose new strategies for designing and synthesizing new LCCs with tailored structures and functions. Looking forward, the ESI-MS method will play increasingly significant roles in LCC research. The continued development of these technologies will deepen the understanding of the structure-property relationships. With the ongoing convergence of computational chemistry and information science, we anticipate more precise design and synthesis of LCCs, leading to broader applications in magnetism, optics, and catalysis.

In Situ Reaction Forms Uniform Mixed Heterometallic LnIII2MnII4 (Ln = DyIII and GdIII) Clusters: Assembly Mechanism and Insights into Performance

The unclear assembly mechanism seriously hinders the preparation and application of 3d-4f heterometallic clusters. Two new heterometallic nanoclusters [Dy2Mn4(HL)4(OAc)6]·5EtOH·H2O (1) and [Gd2Mn4(HL)4(OAc)6]·4EtOH·4H2O (2) were obtained from the in situ condensation reaction of 3-amino-1,2-propanediol with 2-hydroxy-1-naphthaldehyde. The intermediate species in the cluster 1 synthesis process were tracked by time-dependent high-resolution electrospray ionization mass spectrometry (HRESI-MS), further revealing the possible formation mechanism (Dy → DyL2 →DyMn2L2 → DyMn3L2 → DyMn4L3 → Dy2Mn4L4). Magnetic studies indicated that the antiferromagnet LnIII-MnII (Ln = DyIII and GdIII) interaction was operative in both titled clusters. Furthermore, the performance of the clusters was regulated by adjusting the type of rare earth ions (DyIII and GdIII). The research results showed that cluster 2 containing GdIII exhibited an excellent longitudinal relaxation rate (r1) with 1.95 mM-1 s-1 under 0.5 T and a relatively suitable r2/r1 value (3.88), which indicated that it can be used as a new and efficient T1 MR contrast agent. Cluster 1 containing DyIII displayed antipathogenic activities against clinical MRSA strain with an MIC of 32 μg/mL. This work not only provided a reference for revealing the assembly mechanism of 3d-4f heterometallic clusters but also confirmed its potential application in the biomedical field.