Methanol soluble and stable guanosine octamers were successfully achieved via H-bond self-assembly. Through structural conformational design, we developed a new class of guanosine derivatives with modification on guanine (8-aryl) and ribose (2′,3′-isopropylidene). This unique design led to the formation of the first discrete G 8 -octamer with its structure characterized by single crystal X-ray diffraction, MS and NMR spectroscopy. The G 8 -octamer showed unique cation recognition properties, including the formation of a stable Rb + templated G-quadruplex. Based on this observation, further modification on the 8-aryl moiety was performed to incorporate a cross-layer H-bond or covalent linkage. Similar G-octamers were obtained in both cases with structures confirmed by single crystal X-ray diffraction. Furthermore, the covalently linked G-quadruplex exhibited excellent stability even in MeOH and DMSO, suggesting a promising future for this new H-bond self-assembly system in biological and material applications.
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Anion mediated, tunable isoguanosine self-assemblies: decoding the conformation influence and solvent effects
Systematic investigations were performed with various substituted groups at C8 purine and ribose. A series of isoG analogs, C8-phenyl substituted isoG were synthesized and applied for Cs + coordination. The structural proximity between purine and ribose limited pentaplex formation for C8-phenyl substituted isoG derivatives. Based on this observation, deoxy isoG derivative with modification on ribose ( tert -butyldimethylsilyl ether) was applied to assemble with the Cs + cation. Critical solvent (CDCl 3 and CD 3 CN) and anion (BPh 4 − , BARF − , and PF 6 − ) effects were revealed, leading to the controllable formation of various stable isoG pentaplexes, including singly charged decamer, doubly charged decamer, and 15-mer, etc. Finally, the X-ray crystal structure of [isoG 20 Cs 3 ] 3+ (BARF − ) 3 was successfully obtained, which is the first example of multiple-layer deoxy isoG binding with the Cs + cation, providing solid evidence of this new isoG ionophore beyond two-layer sandwich self-assembly.
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- Award ID(s):
- 1665122
- PAR ID:
- 10295412
- Date Published:
- Journal Name:
- Chemical Science
- Volume:
- 12
- Issue:
- 21
- ISSN:
- 2041-6520
- Page Range / eLocation ID:
- 7569 to 7574
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract The prebiotic origins of biopolymers and metabolic co‐factors are key questions in Origins of Life studies. In a simple warm‐little‐pond model, using a drying phase to produce a urea‐enriched solution, we present a prebiotic synthetic path for the simultaneous formation of neopterins and tetrahydroneopterins, along with purine nucleosides. We show that, in the presence of ribose and in a formylating environment consisting of urea, ammonium formate, and water (UAFW), the formation of neopterins from pyrimidine precursors is robust, while the simultaneous formation of guanosine requires a significantly higher ribose concentration. Furthermore, these reactions provide a tetrahydropterin–pterin redox pair. This model suggests a prebiotic link in the origin of purine nucleosides and pterin cofactors that provides a possible deep prebiotic temporal connection for the emergence of nucleic acids and metabolic cofactors.
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Abstract Cesium methylammonium lead iodide (Cs
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Abstract Cesium methylammonium lead iodide (Cs
x MA1−x PbI3) nanocrystals were obtained with a wide range of A‐site Cs‐MA compositions by post‐synthetic, room temperature cation exchange between CsPbI3nanocrystals and MAPbI3nanocrystals. The alloyed Csx MA1−x PbI3nanocrystals retain their photoactive perovskite phase with incorporated Cs content,x , as high as 0.74 and the expected composition‐tunable photoluminescence (PL). Excess methylammonium oleate from the reaction mixture in the MAPbI3nanocrystal dispersions was necessary to obtain fast Cs‐MA cation exchange. The phase transformation and degradation kinetics of films of Csx MA1−x PbI3nanocrystals were measured and modeled using an Avrami expression. The transformation kinetics were significantly slower than those of the parent CsPbI3and MAPbI3nanocrystals, with Avrami rate constants,k , at least an order of magnitude smaller. These results affirm that A‐site cation alloying is a promising strategy for stabilizing iodide‐based perovskites. -
null (Ed.)X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), atomic force microscopy (AFM) and X-ray diffraction (XRD) were applied to investigate the electronic structure and molecular packing of C8-BTBT on HOPG with an ultrathin C 60 interlayer. It was found that C8-BTBT displays a Vollmer–Weber (V–W) growth mode on HOPG, with an ultrathin C 60 interlayer (0.7 nm). Compared to the uniform lying-down growth mode as directly grown on HOPG, the C8-BTBT molecules here adopt a lying-down orientation at low coverage with some small tilt angles because the π–π interaction between C8-BTBT and HOPG is partly disturbed by the C 60 interlayer, delivering a higher highest occupied molecular orbital (HOMO) in C8-BTBT. An interface dipole of 0.14 eV is observed due to electron transport from C8-BTBT to C 60 . The upward and downward band bending in C8-BTBT and C 60 , respectively, near the C8-BTBT/C 60 interface reduces the hole transport barrier at the interface, facilitating the hole injection from C 60 to C8-BTBT, while a large electron transfer barrier from C 60 to C8-BTBT is detected at this interface, which effectively limits electron injection from C 60 to C8-BTBT. The HOMO of C8-BTBT near the interface is largely lifted up by the C 60 insertion layer, which causes a p-doping effect and increases the hole mobility in C8-BTBT. Furthermore, owing to the lowest occupied molecular orbital (LUMO) of C 60 residing in the gap of C8-BTBT, charge transfer occurs between C 60 and the trap states in C8-BTBT to effectively passivate the trapping states. Our efforts aid a better understanding of the electron structure and film growth of anisotropic molecules and provide a useful strategy to improve the performance of C8-BTBT-based devices.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d1sc00988e
