Utsab Manna

White-light emission from simple AIE–ESIPT-excimer tripled single molecular system

A simple organic molecule (L3) has been systematically designed and developed to generate white-light emission from a single-component system. It could also tune several emission colors owing to its diverse spectral nature with varying water fractions in methanol–water and acetonitrile–water mixtures. Essentially, the introduction of an aggregation-induced emission (AIE) phenomenon and excimer-forming ability in the molecular system provided the scope for a dual emission, whereas ESIPT (excited state intramolecular proton transfer) coupled-AIE phenomenon acted as an additional means of adjusting the emission wavelength of the corresponding emission peak by varying the solvent polarity. Detailed AFM (atomic force microscopy), DLS (dynamic light scattering) and X-ray crystallographic studies were carried out to validate the mechanism of generation of white-light emission.

Influence of the cavity dimension on encapsulation of halides within the capsular assembly and side-cleft recognition of a sulfate–water cluster assisted by polyammonium tripodal receptors

The p-nitrophenyl and p-bromophenyl functionalized tris-polyamine receptors, L1 and L2, have formed capsular assembly with halide ions in an encapsulated fashion through efficient hydrogen-bonding. On the other hand, the positional isomer of L1, the m-nitrophenyl functionalized tripodal amine receptor L3, displays a rather flat-open conformation and is unable to bind halide anions in an encapsulated form. The presence of a smaller cavity in these receptors hinders the binding of larger oxyanions like sulfate. As a result, the protonated tripodal scaffold encapsulates small solvent molecules and helps in side-cleft binding of the larger sulfate anion. Herein, we report the design, synthesis and characterization of tren-based polyammonium receptors L1, L2 and L3 and their complexation as well as binding discrepancy with several anions in the presence of acid. The solid state crystal structure of the anion complexes with L1, L2 and L3 reveal that the anions are recognized via stable N–H⋯A, C–H⋯A, anion–π interactions with the protonated receptor molecule in a unimolecular fashion either inside or outside the cavity. The sulfate–water complexes of receptors L1, L2 and L3 are stabilized by (NH)+⋯O type H-bonding and electrostatic interactions among sulfate, water and ammonium groups. The polyammonium based tripodal scaffold with positional variation of the functional group shows significant difference in anion binding fashion through either capsular or non-capsular complex formation.

Anion binding consistency by influence of aromatic meta-disubstitution of a simple urea receptor: regular entrapment of hydrated halide and oxyanion clusters

An electron-withdrawing meta-disubstituted trifluoro-methyl terminal containing bis-urea receptor L derived from meta-phenylenediamine core is logically designed and synthesized for investigating its anion coordination activities. Receptor L has been recognized as a potential system for unusual asymmetric entrapment of naked sulphate anion along with R33(5)-type cyclic hydrated sulphate by one of the three symmetry-independent receptor moieties in a unit cell via hydrogen bonding-activated proton transfer from hydrogen sulphate. In addition, it is effective for fluoride-induced fixation of atmospheric CO2 as an air-stable bicarbonate dimer, linear acetate–water polymeric assembly formation and chair-like (chloride)2–(water)2 assembly construction via H-bonding interactions of eight urea groups of four receptor units. Crystallographic results show that including DMF and DMSO-solvated free receptor structures, all halide and oxyanions noncovalently interact with urea groups of particular receptor moiety via noncooperative interactions irrespective of the anion dimension, which is possibly attributed to the aromatic meta-difunctionalization-driven steric effect of ligand architecture.

Steric influence of adamantane substitution in tris-urea receptor: encapsulation of sulphate and fluoride-water cluster

AbstractTris(2-aminoethyl)amine (tren)-based bulky adamantane group-substituted tris-urea (L) has been developed as the potential tripodal receptor exhibiting strong binding affinities towards small spherical fluoride anion as well as large tetrahedral sulphate anion in its neutral and protonated form, respectively. Structural elucidation reveals that the divalent sulphate ion is fully engulfed inside the complementary space created by two face-to-face oriented symmetry-independent protonated receptors, whereas the smaller fluoride ion is encapsulated as fluoride-water cluster (

Halo-methylphenyl substituted neutral tripodal receptors for cation-assisted encapsulation of anionic guests of varied dimensionality

\hbox {F}^{-}\hbox {-H}_{2}\hbox {O}

An aggregation-induced emission (AIE) active probe for multiple targets: a fluorescent sensor for Zn2+ and Al3+ & a colorimetric sensor for Cu2+ and F−

F--H2O) assemblage within the neutral unimolecular capsular assembly of receptor L.GRAPHICAL ABSTRACTSYNOPSIS Entrapment of Sulphate and fluoride-water cluster within the rigid cavity of adamantine-substituted tris-urea.

Entrapment of Cyclic Fluoride–Water and Sulfate–Water–Sulfate Cluster Within the Self-Assembled Structure of Linear meta -Phenylenediamine Based Bis-Urea Receptors: Positional Isomeric Effect

One of the supreme anion binding building blocks exhibiting strong interplay among topology, complementarity and coordination over the last two decades is the tris(2-aminoethyl)amine skeleton. However, recognition of anions/hydrated anions within the self-assemblies of simplest phenyl-based tris(oxyurea/thiourea) neutral ligands has been underexplored from 1995 and more challenging, mainly because of the lack of π-acidic or electron-withdrawing substituents in aryl terminals, especially in the solid state. Herein, two simple tris(oxyurea) (L1) and tris(thiourea) (L2) electron-rich scaffolds are reported with comparatively less acidic terminal aromatic functionalization but still capable of trapping chair-shaped cyclic water hexamer within the infrequent fluoride encapsulated hexameric L1 core as well as divalent carbonate anion encapsulated dimeric capsular cage of L2via hydroxide ion induced aerial CO2 fixation. Moreover, L1 shows large dihydrogen phosphate dimer [(H2PO4−)2] bound neutral dimeric pseudo-capsular assembly, while the thiourea analogue L2 exhibits chloride and acetate bound unimolecular capsular assembly and divalent sulfate bound dimeric cage via hydrogen-bonding activated proton transfer reaction.

Dual Guest [(Chloride)3-DMSO] Encapsulated Cation-Sealed Neutral Trimeric Capsular Assembly: Meta-Substituent Directed Halide and Oxyanion Binding Discrepancy of Isomeric Neutral Disubstituted Bis-Urea Receptors

Aromatic tripodal anion receptors derived from either flexible [tris(2-aminoethyl)-amine], tren skeletons or any other benzene-based rigid platforms reported from the beginning of anion recognition chemistry contain either electron-withdrawing group/s, electron-donating group/s or zero substituents at the terminal aromatic rings. In this report, we have rationally designed and synthesized two tren-based halo-methylphenyl disubstituted tris-urea receptors, which have one electron-withdrawing halide group (chloro/bromo) as well as one electron-donating methyl group at their terminal aromatic rings. The tris([(3-chloro-4-methylphenyl)amino]ethyl)-urea receptor, L1, efficiently captures spherical chloride and bromide anions in complexes 1a and 1b, respectively, via 1 : 1 cation-sealed host–guest encapsulation, whereas its isomeric tris([(4-bromo-3-methylphenyl)amino]ethyl)-urea receptor, L2, encapsulates the smallest halide anion in complex 2avia formation of unimolecular polymeric host–guest assemblies. In contrast, planar carbonate, tetrahedral sulphate and octahedral hexafluorosilicate anions of varied dimensionalities are engulfed inside the dimeric capsular cages of either of the isomeric neutral receptors L1 or L2 in 2 : 1 host–guest fashion, irrespective of the size of the countercations in complexes 1c, 1d, 2b or 2c.