Spontaner Aufbau einer organisch‐anorganischen Nukleinsäure‐Z‐DNA‐Doppelhelix‐Struktur

State-of-the-art chiroptical spectroscopies are valuable tools for structural elucidation. However, the potential of these spectroscopies for everyday applications has not been exploited to date partially due to the lack of sufficiently stable and efficient chiroptical systems. To this end, the development of suitable chiroptical structures is essential. Herein, we present the synthesis of spiro-compounds (P )-1 and (P )-2 as well as (M )-1 and (M )-2 exhibiting remarkable chiroptical responses. Theoretical simulations show that (P )-1, constituted by two (P)-configured spiranic chiral axes, presents an all-carbon double helix structure with (M)-helicity. On the other hand, molecular dynamic simulations reveal (P )-2 to have a single path for geometry-modification along its flat conformational space, certifying it as a chiral flexible shape-persistent macrocycle. Geometric quantification of chirality has been used to compare the spiranic derivatives presented herein.

Section: Methodsmentioning

confidence: 99%

Diverse Chiral Scaffolds from Diethynylspiranes: All‐Carbon Double Helices and Flexible Shape‐Persistent Macrocycles

Castro‐Fernández

Ren

García

et al. 2017

“…Isomerism is commonly seen in macromolecular systems from biomacromolecules to inorganic clusters such as polyoxometalate (POM) clusters . For well‐defined POM molecular clusters, understanding the stability and transition issues will underpin its applications in biochemistry, drug delivery, catalysis etc. As an example, the geometrical isomers of the Keggin family, depending on the successive 60°‐rotations of the trimeric group, were postulated by Baker and Figgis in 1970 .…”

Section: Figurementioning

confidence: 99%

A Spontaneous Structural Transition of {U₂₄Pp₁₂} Clusters Triggered by Alkali Counterion Replacement in Dilute Solution

Gao

Dembowski

Szymanowski

et al. 2017

At ransition between two isomeric clusters involving the change of the main skeleton structure of aw ell-defined,r igid molecular cluster [(UO 2 ) 24 (O 2 ) 24 (P 2 O 7 ) 12 ] 48À ,{ U 24 Pp 12 }, is achieved by simply introducing propera lkali cationsi nto its dilute aqueouss olution. While the unique structuralt ransition can be triggered by introducing any of the Na + /K + /Rb + /Cs + alkali ions, the two isomers, Li/Na-{U 24 Pp 12 }a nd Na/K-{U 24 Pp 12 }, as typical macroions,c an accurately choose among different alkali counter-cations based on their hydrated sizes, and the ion selectivity process clearlys howed endothermic features.T he preferred K + and Rb + ions have suitable sizes to be incorporated into the properw indows on {U 24 Pp 12 }n anocapsules,a ss upported by the transition points in both ITC studies and IR measurements.Isomerism is commonly seen in macromolecular systems from biomacromolecules to inorganic clusters such as polyoxometalate (POM) clusters.[1] For well-defined POM molecular clusters, understanding the stability and transition issues will underpin its applicationsinb iochemistry, [2] drug delivery, [3] catalysis [4] etc. As an example, the geometrical isomers of the Kegginf amily, depending on the successive 608-rotations of the trimeric group, were postulated by Baker and Figgis in 1970.[5] The unusual structuralf lexibility has led to the efforts for rationalizing the dynamics and stabilityo fK eggin anions.[6] The five anionic isomers, with the same formula, demonstrated different redox properties that vary from each other,w hich made the early investigationst owards triggering the isomeric transition mainly concentrateo nc hanging their redoxs tates, for example, by heatingo ra pplying reductant. [1b, 6b] Furthermore, Kim and Pope reported that the positions of different coordinated cations sandwiched between two A-type R-PW9 Keggins were not alwayst he same, while the structure of the two individual clusters remained untouched.[7] Herein we report an ovel type of isomeric structural transition of the uranyl peroxide clusters, which is triggered and affected by its ion exchange and ion selectivity properties. To the best of our knowledge,t his is, so far,t he mildest and most convenient way of changing the main skeleton of ap olyoxoanion.Counterionsp lay an essential role in regulating the behaviors of soluble macroions and charged nanoparticles in solution.[8] The demands for precise guidance on ions within inorganic nanopores have drawn substantial attention.[9] Exploring the nature of ion selectivity and its consequent effect on macroions, especially their stability, remainsachallenge.T he actinyl peroxide nanocages are ideal modelsf or investigating the macroion-counterion interaction in solution owing to their rigid andp orous structures, good stability, and suitable charge density.[10] The developmento fu ranium-based nanomaterials can also impact the management of nuclear wastes. [11] We probe the ion selectivity and the transition of two isomeric uranyl...

“…More generally, ordered hierarchical assemblies, such as 3D metal–organic frameworks (MOF) structures, 2D superlattice and porous sheets, onion‐like spheres, nanorolls, hollow spindles, 1D nanotubes, and fibrous structures could be created with the assistance of molecular structure‐directing agents. Guanosine‐modified POMs could spontaneously assemble into ordered crystals with a double helix POM arrays . Helical POM nanofibers have also been developed in organic solvents by using chiral or achiral surfactants as structure‐directing agents.…”

Section: Introductionmentioning

confidence: 99%

Short Peptides Directing 1D Helical Arrays of Polyoxometalates with Controllable Pitches

Jiang

et al. 2017

A series of cationic peptides with alternating hydrophilic and hydrophobic residues were elaborately designed and synthesized. These kinds of short peptides with protonated lysine groups can interact with anionic polyoxometalate nanoclusters through multivalent ionic bonds and hydrogen bonds, resulting in the formation of helical polyoxometalate arrays in aqueous solution. Fourier transform infrared (FTIR) spectroscopy, circular dichroism (CD), transmission electron microscopy (TEM), and dynamic light scattering (DLS) were utilized to characterize the self-assembled structures. TEM revealed that the polyoxometalate clusters form periodic arrays within the helical nanofibers. This work reports that the handedness of the helical fibers was attributed to the precise chirality expression of peptides. The l-type peptide directed the formation of left-handed polyoxometalate arrays, whereas right-handed polyoxometalate arrays were observed when the peptide was constituted by d-amino acids. It was also found that the pitch of the helical nanofibers is inversely proportional to the hydrophobicity of peptides with less hydrophobicity giving a larger helical pitch.