Competitive hydrogen bonding of cyclopropenium ions: Implications of an anion switch

Sueur, Richard Le; Guest, Matt; Belding, Lee; Pilkington, Melanie; Dudding, Travis

doi:10.1016/j.tetlet.2019.07.019

Cited by 9 publications

(7 citation statements)

References 22 publications

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“…Based on our previous reports demonstrating counterion effects on cyclopropeniums, e.g., quantum yield and (intra- versus intermolecular) hydrogen bonding and/or reactivity, we next examined trisaminocyclopropenium 6f · BF 4 – to assess if switching the counterion had an influence on fluorescence. Notably, the quantum yield (ϕ = 0.12) of trisaminocyclopropenium 6f · BF 4 – was nearly double that of fluorophore 6f · Cl – , clearly showing the impact of a tetrafluoroborate counterion versus a chloride counterion.…”

Section: Results and Discussionmentioning

confidence: 99%

Trisaminocyclopropenium Cations as Small-Molecule Organic Fluorophores: Design Guidelines and Bioimaging Applications

et al. 2020

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The discovery of fluorescence two centuries ago ushered in, what is today, an illuminating field of science rooted in the rational design of photochromic molecules for task-specific bio-, material-, and medical-driven applications. Today, this includes applications in bioimaging and diagnosis, photodynamic therapy regimes, in addition to photovoltaic devices and solar cells, among a vast multitude of other usages. In furthering this indispensable area of daily life and modern-day scientific research, we report herein the synthesis of a class of trisaminocyclopropenium fluorophores along with a systematic investigation of their unique molecular and electronic dependent photophysical properties. Among these fluorophores, tris[N(naphthalen-2-ylmethyl)phenylamino] cyclopropenium chloride (TNTPC) displayed a strong photophysical profile including a 0.92 quantum yield ascribed to intramolecular charge transfer and intramolecular through-space conjugation. Moreover, this cyclopropenium-based fluorophore functions as a competent imaging agent for DNA visualization and nuclear counterstaining in cell culture. To facilitate the broader use of these compounds, design principles supported by density functional theory calculations for engineering analogs of this class of fluorophores are offered. Collectively, this study adds to the burgeoning interest in cyclopropenium compounds and their unique properties as fluorophores with uses in bioimaging applications.

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Section: Results and Discussionmentioning

confidence: 99%

Trisaminocyclopropenium Cations as Small-Molecule Organic Fluorophores: Design Guidelines and Bioimaging Applications

et al. 2020

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“…The solvent was decanted, and the final product was then washed thoroughly with ether.T he ether was removed under reduced pressure to afford 11 as al ight tan solid in 90 %y ield (1.35 g, 7.99 mmol). 1 HNMR (300 MHz, tert-Butyl-(8-((1,3-dimethylimidazolidin-2-ylidene)amino)naphthalene-1-yl)carbamate (12) To af lame dried 100 mL round bottom flask backfilled with N 2(g) was added 9 (1.27 g, 4.92 mmol) and dry DCM (20.0 mL) followed by ad ropwise addition of triethylamine (1.4 mL, 10.04 mmol). The resulting solution was placed in an ice bath and 11 was added in one batch (1.00 g, 5.92 mmol) at which point the solution was allowed to warm to room temperature and left to stir for 24 hours.…”

Section: Methodsmentioning

confidence: 99%

“…[8,9] In our laboratory, proton sponges and relateds uperbases have been employed as phase-transfer catalysts, [10] small molecule fluorophores, [11] as well as fort he fundamentals tudy of intra-versus intermolecular hydrogen bonding interactions within molecules. [12] As for proton sponges and the factorsc ontributing to high basicity,t he widely accepted criteria for their classification include:( i) free base destabilization arising from proximal nitrogen lone pair-to-lonep air repulsion;( ii)favorable formation of as trong intramolecular hydrogen bond (IMHB)N •••H-N upon protonation;( iii)reliefo fs teric strain in transitioningf rom a non-planar base to as tabilized planar cation, and most recently (iv) the generation of aromaticity upon protonation. [13] Paving the way for the above set of criteria was the discovery of the first protons ponge, 1,8-diaminonaphthalene( DMAN, 1), by Alder in the late 1960s ( Figure 1).…”

Section: Introductionmentioning

confidence: 99%

“…By the same token, proton sponges lend themselves to a broad range of applications that include directing agents for the synthesis of crystalline microporous materials, deprotonating matrices in mass spectrometry, and catalysts or reactants for chemical transformations . In our laboratory, proton sponges and related superbases have been employed as phase‐transfer catalysts, small molecule fluorophores, as well as for the fundamental study of intra‐ versus intermolecular hydrogen bonding interactions within molecules …”

Section: Introductionmentioning

confidence: 99%

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Development of an Unsymmetrical Cyclopropenimine‐Guanidine Platform for Accessing Strongly Basic Proton Sponges and Boron‐Difluoride Diaminonaphthalene Fluorophores

Guest

Sueur

Pilkington

et al. 2020

Chemistry A European J

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An unsymmetrical guanidine-cyclopropenimine proton sponge DAGUN andt he relatedB F 2-chelate DAGBO are reported. Insight into the structural, electronic, bonding and photophysical properties of these two molecules are presented.J oint experimental and theoretical studies reveal the protonated form of DAGUN possessesa ni ntramolecular N•••HÀNh ydrogen bond which affords ah igh experimental pK BH + of 26.6 (computed = 26.3). Photophysical studies show that in solution DAGUN displays ag reen emission at 534 nm, with al arge Stokess hift of 235 nm (14,718 cm À1). In contrast, the conjugate acid DAGUN-H + is only weakly emis-sive due to attenuated intramolecular charge transfer.X-ray diffraction studies revealt hat DAGBO contains as table tetracoordinate boronium cation, reminiscent of the well-established BODIPY family of dyes. In solution, DAGBOe xhibits a strong blue emission at 450 nm coupled with al arge Stokes shift (Dl = 158 nm, Dn = 11,957 cm À1)a nd quantum yield of 62 %, upon excitation at 293 nm. DAGBO sets the stage as the first entry into an ew class of boron-difluoride diaminonaphthalenes (BOFDANs)t hat represent highlyf luorescent and tunable next-generation dyes with future promise for biosensing and bioimaging applications.

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“…TAC salts also have excellent thermal stability, despite the ring strain, due to their aromaticity, charge delocalization, and high‐energy HOMO. Other areas of interest include anion switches, [34] polyurethanes, [35] ionic liquid crystals, [36] polyelectrolytes, [37] phase‐transfer catalysis, [38,39] organocatalysis, [40] hypergolic fluids, [41] and lipase activation [42] . We initially reported the IL properties of TAC‐based salts in 2011, [43] and this was followed by studies on tris(dialkylamino)cyclopropenium (TDAC) NTf 2 − ILs [44] and dicyanamide (DCA) ILs, [45] as well as protic and amino acid‐functionalised TAC ILs [46,47] .…”

Section: Introductionmentioning

confidence: 99%

Highly‐fluorinated Triaminocyclopropenium Ionic Liquids

Curnow

Senthooran

2022

Chemistry An Asian Journal

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A series of highly‐fluorinated triaminocyclopropenium salts, with up to six fluorous groups, were prepared and their properties as ionic liquids investigated. Reaction of pentachlorocyclopropane or tetrachlorocyclopropene with bis(2,2,2‐trifluoroethyl)amine, HN(CH2CF3)2, occurs in the presence of a trialkylamine, NR3, to give cations with two fluorinated amino groups, [C3(N(CH2CF3)2)2(NR2)]+ (R=Et, Pr, Bu, Hex), with traces of [C3(N(CH2CF3)2)3]+. Use of appropriate reagent ratios and reaction times and subsequent addition of a dialkylamine, HNR'R”, gives cations with one fluorinated amino group, [C3(N(CH2CF3)2)(NR2)(NR'R”)]+ ((NR2)(NR'R”)=(NBu2)2, (NEt2)(NPr2), (NBu2)(NBuMe)). These cations were isolated as chloride salts and some of these were converted to bistriflamide, dicyanamide and triflate salts to provide ionic liquids. These salts were characterised by thermal (DSC and TGA) measurements and miscibility/solubility properties (determined in a range of solvents). Ionic liquids (ILs) were also characterised by density, viscosity and conductivity measurements where possible. X‐ray diffraction studies of chloride salts showed the formation of fluorous regions and more hydrophilic ionic regions in the solid state.

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Competitive hydrogen bonding of cyclopropenium ions: Implications of an anion switch

Cited by 9 publications

References 22 publications

Trisaminocyclopropenium Cations as Small-Molecule Organic Fluorophores: Design Guidelines and Bioimaging Applications

Trisaminocyclopropenium Cations as Small-Molecule Organic Fluorophores: Design Guidelines and Bioimaging Applications

Development of an Unsymmetrical Cyclopropenimine‐Guanidine Platform for Accessing Strongly Basic Proton Sponges and Boron‐Difluoride Diaminonaphthalene Fluorophores

Highly‐fluorinated Triaminocyclopropenium Ionic Liquids

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