Acylhydrazone Switches: <i>E/Z</i> Stability Reversed by Introduction of Hydrogen Bonds

Lu, Chaocao; Htan, Bu; Ma, Chunmiao; Liao, Rong‐Zhen; Gan, Quan

doi:10.1002/ejoc.201801466

Cited by 12 publications

(5 citation statements)

References 25 publications

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“…Among them, rare negative photochromic systems have also been demonstrated . The Z isomer of acylhydrazones, usually disfavored, can be stabilized with properly introduced hydrogen bonds . This effect was used for pyridyl acylhydrazones, in switchable cinchona‐derived enantioselective organocatalysts, as well as in the first photoswitchable heteroditopic ion‐pair receptor in which both cation and anion binding sites were simultaneously and reversibly switched …”

Section: Molecular Photoswitchesmentioning

confidence: 99%

Recent Implementations of Molecular Photoswitches into Smart Materials and Biological Systems

Pianowski

2019

Chemistry A European J

287

226

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Light is a nearly ideal stimulus for molecular systems. It delivers information encoded in the form of wavelengths and their intensities with high precision in space and time. Light is a mild trigger that does not permanently contaminate targeted samples. Its energy can be reversibly transformed into molecular motion, polarity, or flexibility changes. This leads to sophisticated functions at the supramolecular and macroscopic levels, from light‐triggered nanomaterials to photocontrol over biological systems. New methods and molecular adapters of light are reported almost daily. Recently reported applications of photoresponsive systems, particularly azobenzenes, spiropyrans, diarylethenes, and indigoids, for smart materials and photocontrol of biological setups are described herein with the aim to demonstrate that the 21st century has become the Age of Enlightenment—“Le siècle des Lumières”—in molecular sciences.

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Section: Molecular Photoswitchesmentioning

confidence: 99%

Recent Implementations of Molecular Photoswitches into Smart Materials and Biological Systems

Pianowski

2019

Chemistry A European J

287

226

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“…Dipyrrinone derivatives 6−14, on the other hand, can form intramolecular hydrogen bonds in both the protonated (6a−12a) and deprotonated (6b−12b) states, due to tautomerization and/ or rotation of the imidazole/pyrazole ring systems; therefore, both the protonated and deprotonated states result in observed fluorescence. Similar restriction of E/Z isomerization, via intramolecular hydrogen bonding, has been described for acyl hydrazones for nonfluorescent compounds, 23,24 and intramolecular hydrogen bonds, which produce constrained rotations, have been reported to enhance intensity of 12.9 a Fluorescence was not detectable for 22. b Quinine (Q = 0.55) 19 and Anthracene (Q = 0.27) 19,20 were used as standards. fluorescence, for a number of systems, including a 7-nitrobenz-2-oxa-1,3-diazole system used to detect cysteine and homocysteine via restriction of C = N bond isomerization, 25 6-propionyl-2-(dimethyamino)naphthalene derivatives in which the inability to form intramolecular hydrogen bonds substantially reduces quantum yields, 26,27 fluorinated pyrazoline analogues where C−H•••F interactions impede molecular motion, 28 and 2-quinolones that form rigid complexation in acidic solutions.…”

Section: ■ Results and Discussionmentioning

confidence: 62%

Pyrazole, Imidazole, and Isoindolone Dipyrrinone Analogues: pH-Dependent Fluorophores That Red-Shift Emission Frequencies in a Basic Solution

et al. 2019

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Dipyrrinones are nonfluorescent yellow-pigmented constituents of bilirubin that undergo Z to E isomerization when excited with UV/blue light. Mechanical restriction of the E/Z isomerization process results in highly fluorescent compounds such as N,N-methylene-bridged dipyrrinones and xanthoglows. This manuscript describes the first examples of dipyrrinone analogues, which exhibit fluorescence without covalently linking the pyrole− pyrrolidine nitrogen atoms. Instead these analogues restrict E/Z isomerization through intramolecular hydrogen bonding, resulting in mild to moderately fluorescent compounds (Φ F = 0.01−0.30). Further, in basic solutions (pH > 12), the dipyrrinone analogues readily deprotonate and absorption/emission profiles of the fluorophores red-shifts by 10−49 nm. Directly from commercial materials, 10 analogues were prepared in 41−96% yields in one step. To estimate the capacity of which intramolecular hydrogen bonding has upon restricting the E/Z isomerization process, conformational energies of all analogues, in both the protonated and deprotonated species, were explored by using quantum-mechanical density functional theory (DFT) and time-dependent DFT calculations. The computed strengths of the intramolecular hydrogen bonds are related to the barriers of rotation about the 5−6 bond and both correlate with the experimentally measured fluorescence quantum yields.

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“…The introduction of more than one hydrazonic subunit within the same molecule can give superior functions, e.g., sensor action, bioactivity, or biding capacity, in comparison with the monohydrazone compounds [17,18]. This is intrinsically related to greater isomeric and tautomeric prosperity as well as redox activity of the systems [19][20][21]. Such behavior can be even more pronounced if the molecular fragments connecting hydrazone subunits are flexible (e.g., alkyl joints), as they allow spatially separated hydrazone parts to approach closely [18,22,23].…”

Section: Introductionmentioning

confidence: 99%

Succinyl and Adipoyl Dihydrazones: A Solid-State, Solution and Antibacterial Study

et al. 2022

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A series of aryl-functionalized alkyl dihydrazones was prepared by condensation of succinyl or adipoyl dihydrazide and selected ortho-hydroxybenzaldehydes (2-hydroxybenzaldehyde, 2-hydroxy-1-naphthaldehyde, 2,3-dihydroxybenzaldehyde, and 2,4-dihydroxybenzaldehyde) in solution. The obtained products were structurally characterized in the solid state by single-crystal X-ray diffraction (SC-XRD), thermal analysis (TGA-DSC), and Fourier transform infrared (FTIR) spectroscopy and in DMSO-d6 solution by nuclear magnetic resonance (NMR) techniques. Combined FTIR and crystal structure data point to a N–NH–C=O tautomeric form of the hydrazone parts as well as the enol-imino tautomeric form of the aldehyde residues and a robust trans-syn conformation for the structurally investigated ones. While the molecules retain the same tautomeric form in the DMSO-d6 solution, they adopt several conformations, due to rotations around Car–C, C–N, and N–N bonds. The compounds show exceptional thermal stability, with a complex degradation pattern. Slight differences in thermal behavior correlate to alkyl chain length and aryl substituents. The in vitro cytotoxic activity of prepared dihydrazones was evaluated on THP-1 and HepG2 cell lines, while their antibacterial activity was tested against Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, and Moraxella catarrhalis bacteria. All compounds proved to be non-cytotoxic, and some exhibited moderate antibacterial activity.

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Acylhydrazone Switches: E/Z Stability Reversed by Introduction of Hydrogen Bonds

Cited by 12 publications

References 25 publications

Recent Implementations of Molecular Photoswitches into Smart Materials and Biological Systems

Recent Implementations of Molecular Photoswitches into Smart Materials and Biological Systems

Pyrazole, Imidazole, and Isoindolone Dipyrrinone Analogues: pH-Dependent Fluorophores That Red-Shift Emission Frequencies in a Basic Solution

Succinyl and Adipoyl Dihydrazones: A Solid-State, Solution and Antibacterial Study

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