Conformational adjustments over synthons of urea and thiourea based assemblies

Phukan, Nithi; Baruah, Jubaraj B.

doi:10.1039/c6ce01326k

Cited by 14 publications

(13 citation statements)

References 75 publications

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“…Conformation adjustments in different organic crystals of flexible organic compounds occur due to weak solute‐solvent interactions encountered during crystallization to adopt a tight packed structure. This is possible as weak non‐covalent interactions have comparable energies to cause conformation changes such that it is neither the conformer of lowest energy state nor the highest energy but an intermediate one . In the present study the cationic part in the structure of the salts show different conformational adjustments.…”

Section: Resultsmentioning

confidence: 99%

Changes in Emission Properties by π‐Stacking and Conformation Adjustment of an Imidazole‐Tethered Naphthalimide Derivative

2018

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Solid state self-assemblies of 2,4-dinitrophenolate, 2,4,6-trinitrophenolate salts of N-(3-imidazol-1-yl-propyl)-1,8-naphthalimide (abbreviated as imidanap) have distinguishable p-stacking patterns, each stack influences fluorescence emission causing fluorescence quenching. It is found that the solid sample of nitrate or bromide salt of imidanap retains fluorescence properties of the parent compound. Photo-induced electron transfer process in solution gets prominence upon interactions of imidanap with hydrobromic as well as nitric acid but in the nitrophenolate salts the effect of p-interactions over-ride the effect of protonation of imidazole to change intensity of fluorescence emission. DFT calculations using B3LYP functional with 6-31 + G (d,p) as basis set have revealed LUMO in the imidanap and in the respective nitrophenolate salts are localized on the naphthalimide unit whereas HOMO in each case is localization differently over the rings other than the naphthalimide ring. Studies based on 1 H NMR suggest that water causes conformation adjustments of imidanap by forming hydrogen bonds. This enhances photo-induced electron transfer (PET) emission of the imidanap until a limiting concentration of water is reached, beyond which increase in amount of water causes quenching of emission. The PET-ON state of imidanap generated by addition of water to an acetonitrile solution is quenched by 2,4,6-trinitrophenol due to charge-transfer interactions.

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Section: Resultsmentioning

confidence: 99%

Changes in Emission Properties by π‐Stacking and Conformation Adjustment of an Imidazole‐Tethered Naphthalimide Derivative

2018

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“…Beside these, the non‐covalent self‐assemblies of multi‐functional compounds are challenging as there are more numbers of hydrogen bond sites and related supramolecular interactions makes different local envionments . Slight variations in crystallization conditions changes conformation, and yield conformational polymorphs . For example, while crystallization of pyridinium salt of carboxylic acid subtle changes in the crystallization conditions lead to polymorphs .…”

Section: Introductionmentioning

confidence: 99%

“…[9][10][11][12] Slight variations in crystallization conditions changes conformation, [13][14] and yield conformational polymorphs. [15][16][17] For example, while crystallization of pyridinium salt of carboxylic acid subtle changes in the crystallization conditions lead to polymorphs. [18] The chargeassisted hydrogen bonds introduced by Gilli and Gilli are of interest as they could make hierarchical affect over the many weak supramolecular interactions.…”

Section: Introductionmentioning

confidence: 99%

Neutral, Zwitterion, Ionic Forms of 5‐Aminoisophthalic Acid in Cocrystals, Salts and Their Optical Properties

2019

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Different ionic and zwitterionic forms of amphoteric 5‐aminoisophthalic acid were observed in the self‐assemblies of five salts and in a cocrystal. The presence of these forms of the molecule caused differences in respective local environments, which were reflected in corresponding absorption and emission spectra in solid state. Dianion of the acid was observed in hydrated 1:2 salt with 6‐methylpyridin‐2‐amine whereas the salt of 5‐methylthiazol‐2‐amine had the zwitterionic anion. The mono‐anion of the 5‐aminoisophthalic acid was observed in the salt of 4,6‐dimethylpyrimidin‐2‐amine. The self‐assembly of the 1:1 cocrystal of caffeine with 5‐aminoisophthalic acid had neutral form of the acid and the cationic form of the acid was observed in the perchlorate and bromide salts. DFT‐calculation with using CAMB3LYP functional with 6–31+G (d,p) as basis set in gas‐phase showed that different HOMO‐LUMO gaps of the neutral, cation and anion forms and these were reflected in the corresponding UV‐visible spectra of the salt. The changes in intra‐molecular charge transfer (ICT) fluorescence emissions in solid samples due to the different ionic forms were demonstrated.

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“…12% shorter than the sum of the van der Waals radii of S and H (3.09 Å) [ 73 ] and compatible with weak hydrogen bonds [ 78 ]. Intermolecular NH···S interactions have been observed before for thiourea-type derivatives [ 79 ]. The bond lengths and angles of the 1,2,4-triazoline-5-thione unit of 6 ′ = S are very similar to those reported for simple alkyl-substituted examples such as 1,4-dimethyl-1,2,4-triazole-5-thione ( 4 = S) [ 80 ].…”

Section: Resultsmentioning

confidence: 95%

Coinage Metal Complexes of the Carbenic Tautomer of a Conjugated Mesomeric Betaine Akin to Nitron

et al. 2017

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This study was motivated by our recent observation that the analytical reagent Nitron (2) is an “instant carbene”, whose reaction with coinage metal salts MX afforded complexes of its carbenic tautomer 1,4-diphenyl-3-phenylamino-1,2,4-triazol-5-ylidene (2′). Our aim was to establish an alkyl homologue of 2 in order to achieve a carbenic tautomer of higher donicity. For this purpose 1-tert-butyl-4-methyl-1,2,4-triazol-4-ium-3-tert-butylaminide (6) was synthesized. Its reactions with MX afforded complexes of the carbenic tautomer 1-tert-butyl-3-tert-butylamino-4-methyl-1,2,4-triazol-5-ylidene (6′). With a stoichiometric ratio of 1:1 complexes of the type [MX(6′)] were obtained. A ratio of 2:1 furnished complexes of the type [MX(6′)2] or [M(6′)2]X. 6′ is a better σ-donor and less electrophilic than 2′ according to NMR spectroscopic data of 6H[BF4] and 6′ = Se, respectively, and IR spectroscopic data of [RhCl(6′)(CO)2] confirm that its net electron donor capacity is superior to that of 2′. A comparison of the complexes of 2′ and 6′ reveals two pronounced structural differences. [CuX(6′)2] (X = Cl, Br) exhibit more acute C–Cu–C bond angles than [CuX(2′)2]. In contrast to [CuCl(2′)], [CuCl(6′)] aggregates through Cu···Cu contacts of ca. 2.87 Å, compatible with cuprophilic interactions. These differences may be explained by the complementary steric requirements of the t-Bu and the Me substituent of 6′.

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Conformational adjustments over synthons of urea and thiourea based assemblies

Cited by 14 publications

References 75 publications

Changes in Emission Properties by π‐Stacking and Conformation Adjustment of an Imidazole‐Tethered Naphthalimide Derivative

Changes in Emission Properties by π‐Stacking and Conformation Adjustment of an Imidazole‐Tethered Naphthalimide Derivative

Neutral, Zwitterion, Ionic Forms of 5‐Aminoisophthalic Acid in Cocrystals, Salts and Their Optical Properties

Coinage Metal Complexes of the Carbenic Tautomer of a Conjugated Mesomeric Betaine Akin to Nitron

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