skip to main content

Title: On the Search of a Silver Bullet for the Preparation of Bioinspired Molecular Electrets with Propensity to Transfer Holes at High Potentials
Biological structure-function relationships offer incomparable paradigms for charge-transfer (CT) science and its implementation in solar-energy engineering, organic electronics, and photonics. Electrets are systems with co-directionally oriented electric dopes with immense importance for CT science, and bioinspired molecular electrets are polyamides of anthranilic-acid derivatives with designs originating from natural biomolecular motifs. This publication focuses on the synthesis of molecular electrets with ether substituents. As important as ether electret residues are for transferring holes under relatively high potentials, the synthesis of their precursors presents formidable challenges. Each residue in the molecular electrets is introduced as its 2-nitrobenzoic acid (NBA) derivative. Hence, robust and scalable synthesis of ether derivatives of NBA is essential for making such hole-transfer molecular electrets. Purdie-Irvine alkylation, using silver oxide, produces with 90% yield the esters of the NBA building block for iso-butyl ether electrets. It warrants additional ester hydrolysis for obtaining the desired NBA precursor. Conversely, Williamson etherification selectively produces the same free-acid ether derivative in one-pot reaction, but a 40% yield. The high yields of Purdie-Irvine alkylation and the selectivity of the Williamson etherification provide important guidelines for synthesizing building blocks for bioinspired molecular electrets and a wide range of other complex ether conjugates.  more » « less
Award ID(s):
Author(s) / Creator(s):
; ; ; ; ; ;
Date Published:
Journal Name:
Page Range / eLocation ID:
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract “Biomimetic” and “bioinspired” define different aspects of the impacts that biology exerts on science and engineering. Biomimicking improves the understanding of how living systems work, and builds tools for bioinspired endeavors. Biological inspiration takes ideas from biology and implements them in unorthodox manners, exceeding what nature offers. Molecular electrets, i.e. systems with ordered electric dipoles, are key for advancing charge-transfer (CT) science and engineering. Protein helices and their biomimetic analogues, based on synthetic polypeptides, are the best-known molecular electrets. The inability of native polypeptide backbones to efficiently mediate long-range CT, however, limits their utility. Bioinspired molecular electrets based on anthranilamides can overcome the limitations of their biological and biomimetic counterparts. Polypeptide helices are easy to synthesize using established automated protocols. These protocols, however, fail to produce even short anthranilamide oligomers. For making anthranilamides, the residues are introduced as their nitrobenzoic-acid derivatives, and the oligomers are built from their C- to their N-termini via amide-coupling and nitro-reduction steps. The stringent requirements for these reduction and coupling steps pose non-trivial challenges, such as high selectivity, quantitative yields, and fast completion under mild conditions. Addressing these challenges will provide access to bioinspired molecular electrets essential for organic electronics and energy conversion. 
    more » « less
  2. null (Ed.)
    Abstract Biomimicry, biomimesis and bioinspiration define distinctly different approaches for deepening the understanding of how living systems work and employing this knowledge to meet pressing demands in engineering. Biomimicry involves shear imitation of biological structures that most often do not reproduce the functionality that they have while in the living organisms. Biomimesis aims at reproduction of biological structure-function relationships and advances our knowledge of how different components of complex living systems work. Bioinspiration employs this knowledge in abiotic manners that are optimal for targeted applications. This article introduces and reviews these concepts in a global historic perspective. Representative examples from charge-transfer science and solar-energy engineering illustrate the evolution from biomimetic to bioinspired approaches and show their importance. Bioinspired molecular electrets, aiming at exploration of dipole effects on charge transfer, demonstrate the pintail impacts of biological inspiration that reach beyond its high utilitarian values. The abiotic character of bioinspiration opens doors for the emergence of unprecedented properties and phenomena, beyond what nature can offer. 
    more » « less
  3. This study examines how the inherent diffusion constraints of MFI (3D, pore-limiting diameter (PLD) = 0.45 nm), BEA (3D, PLD = 0.60 nm), and MOR (1D, PLD = 0.65 nm) zeolite architectures, at both nanocrystal (nMFI, nBEA, nMOR; d crystal < 0.5 μm) and microcrystal (μBEA, μMOR; d crystal > 0.5 μm) scales, impact functions of mesopores in their hierarchical analogs. Reactivities, deactivation rates, and product selectivities were compared among zeolites, as well as to a mesoporous aluminosilicate control (Al-MCM-41; PLD = 6.2 nm), during Friedel–Crafts alkylation of 1,3,5-trimethylbenzene (TMB; d vdW = 0.72 nm) with benzyl alcohol (BA; d vdW = 0.58 nm) to form 1,3,5-trimethyl-2-benzylbenzene (TM2B; d vdW = 0.75 nm). Operation in the neat liquid phase ([TMB] 0  : [BA] 0 = 35 : 1, 393 K) ensured that the parallel BA self-etherification to yield dibenzyl ether (DBE; d vdW = 0.58 nm) occurred only at the expense of TM2B production when the alkylation reaction was impeded due to hindered access of TMB to confined protons. Investigation of secondary TM2B formation from reaction of DBE with TMB at low [BA]/[DBE] indicates an additional route of selectivity control for hierarchical zeolites that can achieve high BA conversion ( X BA > 0.9) with no DBE cofeed. These findings highlight a compounding advantage of increased diffusivity in mesopores that alter rates, extend lifetimes, and subsequently permit secondary reactions that enable significant shifts in product distribution. Fundamental insights into hierarchical zeolite reaction–diffusion–deactivation for alkylation of poly-substituted aromatics, as detailed here, can be applied broadly to reactions of other bulky species, including biomass-derived oxygenates, for more atom-efficient chemical and fuel production. 
    more » « less
  4. The stepwise synthesis of monodisperse polyethylene glycols (PEGs) and their derivatives usually involves using an acid-labile protecting group such as DMTr and coupling the two PEG moieties together under basic Williamson ether formation conditions. Using this approach, each elongation of PEG is achieved in three steps – deprotection, deprotonation and coupling – in two pots. Here, we report a more convenient approach for PEG synthesis featuring the use of a base-labile protecting group such as the phenethyl group. Using this approach, each elongation of PEG can be achieved in two steps – deprotection and coupling – in only one pot. The deprotonation step, and the isolation and purification of the intermediate product after deprotection using existing approaches are no longer needed when the one-pot approach is used. Because the stepwise PEG synthesis usually requires multiple PEG elongation cycles, the new PEG synthesis method is expected to significantly lower PEG synthesis cost. 
    more » « less
  5. null (Ed.)
    Carbon dioxide based polymers synthesized from the metal-catalyzed copolymeriation of epoxides and CO 2 containing the terpyridine ligand as an end group are reported. The strategy used was to carry out the polymerization in the presence of a carboxylic acid derivative of terpyridine, 4′-(4-carboxyphenyl)-2,2′:6′,2′′-terpyridine (HL), as a chain transfer agent. The epoxide monomer possessing a vinyl substituent, allyl glycidyl ether (AGE), was copolymerized with CO 2 employing a (salen)Co( iii ) catalyst to afford a polycarbonate which upon the addition of mercaptoacetic acid across the double bond, followed by deprotonation, yielded a water soluble polymer. In a similar manner, the sequential formation of a diblock terpolymer produced from propylene oxide, AGE, and CO 2 provided a amphiphilic polycarbonate which self-assembled upon addition to water to form micelle nanostructures. The molecular weights of these CO 2 -derived polycarbonates were shown to be easily controlled by the quantity of chain transfer agent used. These polymeric ligands were demonstrated to provide a modular design for synthesizing a wide variety of metal complexes as illustrated herein for zinc and platinum derivatives. 
    more » « less