AIEE Active Donor–Acceptor–Donor-Based Hexaphenylbenzene

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AIEE Active Donor−Acceptor−Donor-Based Hexaphenylbenzene Probe for Recognition of Aliphatic and Aromatic Amines Subhamay Pramanik, Harnimarta Deol, Vandana Bhalla,* and Manoj Kumar* Department of Chemistry, UGC Sponsored Centre for Advanced Studies-II Guru Nanak Dev University, Amritsar 143005, Punjab, India S Supporting Information *

ABSTRACT: In the present investigation, an intramolecular charge transfer (ICT) and aggregation induced emission enhancement (AIEE) active donor−acceptor−donor (D-A-D) system 5 having fumaronitrile as the acceptor and hexaphenylbenzene (HPB) as the donor moieties joined through rotatable phenyl rings has been designed and synthesized that is highly emissive in the solid state and exhibits stimuli-responsive reversible piezochromic behavior upon grinding and heating. Because of its AIEE characteristics, HPB derivative 5 undergoes aggregation to form fluorescent aggregates in mixed aqueous media that exhibit ratiometric fluorescence response toward aliphatic amines (primary/secondary/tertiary) and turn-off response toward aromatic amines and hence differentiates between them. Further, the solution-coated portable paper strips of derivative 5 showed pronounced and sensitive response toward aromatic and aliphatic amines with a detection limit in the range of picogram and nanogram level, respectively. KEYWORDS: hexaphenylbenzene, ICT, AIEE, piezochromic, porous aggregates, aliphatic and aromatic amines

1. INTRODUCTION Organic amines are important because of their widespread applications in dyeing, the pharmaceutical industry, and materials chemistry.1−4 Some of the aliphatic amines such as triethylamine and hydrazine are used in military operations and as fuel additives in rocket and fighter jet propulsion systems because of their explosive nature.5−7 Despite the versatile applications of organic amines, these amines have ambiguous properties and when present in excess, these amines are toxic and hazardous to the environment and human health. The vapors of toxic organic amines can diffuse into air and enter in to the water bodies from ignition of garbage, construction materials, contaminated water, car exhaust, industrial waste, unexploded explosives and can cause severe health problems such as headaches, skin burns, eye irritation, various respiratory diseases, and even bladder cancer.8 Hence, to ensure a safe working environment, the concentrations of aliphatic/aromatic amines should be monitored in air and wastewater with the assistance of efficient, fast and reliable techniques. The conventional methods for the detection of vapors of amines require sophisticated instrumentations9−12 and these methods suffer from various limitations such as clumsy pretreatment of sample and interference from other volatile compounds. Recently, a variety of fluorescent materials/probes13−20 have been reported that exhibit great potential for the rapid detection of organic amines. However, most of these reported probes suffer from limitations such as poor sensitivity, irreversible response, photobleaching in aqueous media and © XXXX American Chemical Society

turn-off response toward organic amines. Furthermore, these probes lack in selectivity and could not differentiate between aliphatic and aromatic amines during the sensing event.21−24 To date, there are only few reports regarding the development of gel-based materials25−27 and a supramolecular organic framework28 that could differentiate between aliphatic and aromatic amines. However, all the reported supramolecular gels were prepared by aggregation of molecules in organic solvents, which restrict their real time applications for detection of amines in aqueous media. Further, in all these gels, analyteinduced emission changes are centered on single wavelength. For practical applications, materials showing emission changes centered on two different wavelengths (ratiometric) are advantageous because they provide built-in correction and the ratio of two emission bands will be utilized to quantity amine concentration. Thus, the development of highly selective and highly sensitive ratiometric fluorescent material which could discriminate between aliphatic and aromatic amines in solution and vapor phase is still a challenge. Our research work involves the development of fluorescent supramolecular aggregates for trace detection of metal ions,29 anions,30 nitroaromatics,31 and biomolecules32 in solution and Special Issue: AIE Materials Received: July 6, 2017 Accepted: October 18, 2017

A

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ACS Applied Materials & Interfaces Scheme 1. Synthesis of HPB Derivative 5

aliphatic amines in aqueous media. The donor methoxy groups contribute significantly toward enhancing the capability of the supramolecular aggregates to differentiate between aliphatic and aromatic amines. Interestingly, supramolecular assemblies could differentiate between tertiary/secondary/primary aliphatic amines and electron donating/electron withdrawing aromatic amines. Fourth, the supramolecular self-assembled system being reported in this manuscript demonstrates superior sensitivity and remarkable selectivity for instant detection of aliphatic and aromatic amines in vapor phase. The solutioncoated paper strips of 5 could detect aliphatic (triethylamine) and aromatic (aniline) amines with a detection limit in the range of ∼1.01 ng/cm2 and 9.3 pg/cm2, respectively. In comparison to the other probes reported in the literature, the fluorescent self-assembled system being reported in this manuscript for recognition of aliphatic and aromatic amines is rapid, selective, highly sensitive, portable, and low-cost sensory system (Table S2).

in vapor phases. In continuation of this work, we were then interested in the development of supramolecular assemblies which could exhibit sensitive response toward organic amines in aqueous media and could discriminate between aliphatic and aromatic amines. We envisaged that a donor−acceptor−donor system having AIEE characteristics33 could be a good choice for designing these supramolecular assemblies. We focused on a donor−acceptor−donor (D-A-D) scaffold because of the known capabilities of such systems to exhibit analytes dependent changes in their photophysical properties which are clearly visible to naked eye.34 In view of this, in the present investigation, we have designed and synthesized derivative 5 by covalently linking fumaronitrile moiety (acceptor) to methoxy substituted hexaphenylbenzene groups through rotatable phenyl spacers. We envisaged that due to the presence of AIEE29−33 active HPB units, compound 5 will form fluorescent supramolecular assemblies in mixed aqueous media and due to the difference in HOMO energy level and basicity/H-bonding abilities of different types of organic amines, supramolecular assemblies of methoxy substituted derivative 5 may differentiate between aromatic and aliphatic amines. Further, a fumaronitrile moiety is incorporated because of its known versatile electrontransporting properties.35,36 Interestingly, derivative 5 exhibited strong solid-state emission and showed sensitive, selective, and fast response toward organic amines. The work presented in this article has many advantages: first, it represents a simple design for the preparation of an AIEE-ICT active fumaronitrilebased HPB derivative 5 which is highly emissive in solid state and exhibits stimuli responsive reversible piezochromic phenomena. To the best of our knowledge, this is the first report where hexaphenylbenzene based orange emissive compound 5 undergoes piezochromic characteristics (Table S1). Second, derivative 5 undergoes aggregation in mixed aqueous media and forms fluorescent porous spherical aggregates having pore diameter in the range of 1.3 nm, which showed complete quenching of emission in the presence of aromatic amines. The presence of acceptor fumaronitrile and donor methoxy groups tune the energy of the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) of HPB, thus, favor efficient electron transfer from aromatic amines to the molecules within the aggregates. Third, aggregates of derivative 5 show ratiometric response toward

2. RESULTS AND DISCUSSION 2.1. Synthesis and Characterization of HPB Derivative 5. The Sonogashira cross coupling of compound 137 with phenylacetylene 2 catalyzed by PdCl2(PPh3)2 and CuI furnished compound 338 in 75% yield (Figures S35−S38) which on Diels−Alder reaction with 3,4-bis(4-methoxyphenyl)2,5 diphenylcyclopenta-2,4-dienone 4a39 furnished the target compound 5 in 50% yield (Scheme 1). The 1H NMR spectrum of compound 5 showed nine doublets at 7.76 (1H), 7.64 (1H), 7.57 (2H), 7.47 (1H), 7.22 (2H), 7.04 (2H), 6.73 (6H), 6.51(1H) and 6.45 (4H) ppm; two triplets at 7.12 (2H), 6.64 (2H) ppm and two multiplets at 7.40−7.33 (6H), 6.96−6.80 (24H) ppm corresponding to aromatic protons and a singlet at 3.65 ppm (12H) corresponding to methoxy protons. The ESI-MS spectrum showed major peak at m/z = 1285.4919 corresponding to [M + Na]+. The FT-IR spectrum of derivative 5 showed two stretching bands at 2218 (nitrile) and 1030 cm−1 (methoxy O−CH3). All these spectroscopic data support the formation of compound 5 (Figures S39−S42). 2.2. Photophysical Properties of Compound 5. The compound 5 in pure THF exhibits absorption bands at 282 and B

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ACS Applied Materials & Interfaces 372 nm in the UV−vis spectrum due to π−π* transition and intramolecular charge transfer (ICT) transition from donor methoxy groups to the fumaronitrile core (Figure S1). In the fluorescence spectrum, compound 5 exhibits a broad emission band at 455 nm (Φ = 0.32) in THF on excitation at 372 nm (Figure S2 and Table S3). On changing the solvent from hexane, toluene, THF, DCM to DMSO, the absorption behavior of the molecule 5 remained unchanged, thus, indicating the presence of very stable ground state with negligible intramolecular charge transfer process (Figure S3A). In contrast, compound 5 shows positive solvatochromism as significant bathochromic shift (from 395 to 490 nm, Δλem = 95 nm) was observed in the emission spectra of the molecule upon changing the solvent from nonpolar solvent hexane to polar solvent dimethyl sulfoxide (Figure S3B and Table S4). 2.3. Electrochemical Properties and DFT Calculations. To understand the electrochemical behavior of derivative 5 in the ground state, we examined the cyclic voltammogram (CV) of derivative 5 in DCM. Derivative 5 shows irreversible electrochemical behavior and exhibits single oxidation peak which is attributed to the oxidation of the donor HPB units (Figure S4 and Table S5).40,41 For better understanding of the geometry and the electronic structure of derivative 5, we carried out density functional theory (DFT) calculations in gas phase using B3LYP/6-31G(d) as basic set in the Gaussian 09 program (Figure 1). These

studies show that HOMO (−5.662 eV) is localized around the phenyl rings bearing terminal methoxy groups42 and LUMO (−3.113 eV) is centered around the fumaronitrile core. The dihedral angle of the fumaronitrile acceptor core and the donor peripheral HPB unit was found to be around 22.85°. On the basis of these observations, we believe that the twisted spatial conformation of the molecules hinder the intermolecular π−π interactions in derivative 5, thus making the molecule emissive in the bulk phase.43 2.4. Supramolecular Aggregation of HPB Derivative 5. The presence of AIEE active HPB moieties in derivative 5 prompted us to examine its aggregation behavior in mixed aqueous media. The UV−vis spectrum of compound 5 in THF exhibits an absorption band at 372 nm which on gradual addition of water fraction up to 80%, was red-shifted to 378 nm and level-off tails appeared in the visible region (400−500 nm) (Figure 2A). The fluorescence spectrum of derivative 5 in THF exhibits an emission band at 455 nm (Φ0% = 0.32) corresponding to ICT state (λex = 372 nm). Furthermore, on addition of water content up to 30% to that solution, the intensity of the emission band at 455 nm (ICT band) decreases and a new emission band appears at 550 nm. The decrease in emission at 455 nm is due to restriction of ICT in aqueous media and the formation of a new band at 550 nm is due to aggregation of derivative 5 (Figure 2B). Upon addition of water fraction up to 80%, the intensity of emission band at 550 nm increased gradually (Φ80% = 0.65), whereas the emission band at 455 nm disappeared completely. These studies support the AIEE characteristics of derivative 5. We also carried out viscosity dependent fluorescence studies of derivative 5 with increasing fraction of glycerol in DMSO. It was observed that there was enhancement in emission intensity along with red shift from 490 to 520 nm on increasing the concentration of glycerol in DMSO. We also carried out temperature-dependent studies of derivative 5 in H2O/THF (8:2, v/v) media. It was observed that the emission intensity at 550 nm decreases on increasing the temperature from 25 to 75 °C of the solution along with blue shift from 550 to 530 nm. These results clearly suggest that restriction in intramolecular rotation (RIR) is the main reason for the emission enhancement in case of these derivative 5 (Figure S5). The timeresolved fluorescence spectrum of derivative 5 in THF showed a biexponential decay with average lifetime of 0.2634 ns. Upon addition of 80% water fraction to the THF solution of

Figure 1. Energy levels of HOMO and LUMO, energy gaps (Eg), and electron cloud distributions of derivative 5 calculated by the B3LYP/631G(d) method.

Figure 2. (A) UV−vis and (B) fluorescence spectra showing the change in absorption intensity of derivative 5 (5.0 μM) in various H2O/THF mixtures (0−80% volume fraction of water in THF); λex = 372 nm. Inset of B showing the photographs with different water fractions under 365 nm UV lamp illumination. C

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Figure 3. (A−C) TEM images, circles and arrows indicate fusion of spheres; (D, E) TEM and SEM image showing porous spherical nanoassemblies H2O/THF (8:2, v/v) media; (F) 2D SAXS pattern of aggregates of derivative 5.

Scheme 2. Schematic Presentation Shows the Generation of Porous Spherical Nanoassemblies of Derivative 5 in Mixed Aqueous Media

upfield shift (0.04 ppm) of aromatic protons which suggests the presence of intermolecular π−π stacking in derivative 5 (Figure S7). The transmission electron microscopic (TEM) images of HPB derivative 5 show fusion of smaller spheres to generate porous spherical nanoassemblies in H2O/THF (8:2, v/v) media (Figure 3A−D).44−46 The scanning electronic microscopic (SEM) also show the formation of porous spherical nanoassemblies (Figure 3E). The two-dimensional small-angle X-ray scattering (SAXS) pattern of derivative 5 shows a diffuse ring (Figure 3F) and a sharp peak is observed at 0.195 Å−1

derivative 5, the average lifetime of derivative 5 increased significantly (1.778 ns) (Figure S6). The fluorescence radiative rate constants (kf) of derivative 5 increased slightly from 3.4 × 108 s−1 to 3.6 × 108 s−1, on changing the solvent system from THF to H2O/THF (8:2, v/v) mixture, however, nonradiative decay constant (knr) decreased significantly from 3.45 × 109 s−1 to 1.96 × 108 s−1 (Table S6). On the basis of these studies, we propose that the deactivation of nonradiative decay due to restriction of the intramolecular rotational relaxation of the rotors linked to the core is the principal reason for the observed AIEE phenomena in case of derivative 5. Furthermore, the concentration dependent 1H NMR studies showed the average D

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Figure 4. (A) Change in solid-state fluorescence of derivative 5 under grinding and thermal annealing; (B, C) stimuli-responsive behaviors of compounds 5 at solid state upon grinding and heating treatments (under UV lamp, λex = 365 nm); (D) PXRD patterns of solid compounds 5: solid powder, ground powder, ground powder after thermal annealing.

Figure 5. (A) Fluorescence spectra of derivative 5 showing quenching upon addition of aniline (C6H5NH2, 9.0 equiv.) in H2O/THF (8:2, v/v) solution (buffered with HEPES, pH 7.05), λex = 372 nm; Inset of A shows the photographs of (i) before and (ii) after addition of aniline. (B) Change in fluorescence intensity upon addition of aniline (9.0 equiv.) to derivative 5.

2.6. Piezochromic/Mechanochromic Behavior of Compound 5. D-A-D based ICT-AIEE active compound 5 was found to exhibit solid state emission53 with emission maxima at 550 nm (Figure 4A). The powder X-ray diffraction (PXRD) pattern of the derivative 5 showed sharp and intense diffraction pattern, thus, indicating a microcrystalline structure.54,55 After applying pressure/grinding with spatula/pestle, the emission color of the sample changed to yellow (Figure 4B, C) and emission peak blue-shifted to 530 nm. Further, broad reflection pattern was observed in PXRD which indicates the rupture of ordered state i.e., amorphous nature of the compound in the ground state and inhibition of AIEE characteristics (Figure 4D).56 However, upon heating the ground sample of derivative 5 at 150 °C for 5 min, the original emission spectrum and sharp intense reflection peaks were recovered in PXRD pattern which indicates the restoration of the ordered crystalline structure (Figure 4D). The red shifting of emission band under thermal condition is attributed to much stronger π−π interactions and closer chromophoric packing within the molecules.57,58 The transformation of solid to ground solid sample is directly related to the change in molecular packing between well-defined ordered state and a poorly organized phase through treatment of grinding (disruption of molecular packing) and thermal annealing (recovery of ordered molecular packing). The reversible switching of the emission color could be easily recognized by repeating the grinding and heating processes up

(which corresponding to a d-spacing of about 3.2 nm) indicates formation of spherical nanoassemblies (Figure S8).47 The dynamic light scattering studies (DLS) support the formation of porous spherical nanoassemblies of derivatives 5 having average diameter around 350 nm (Figure S9). All the above results show that derivative 5 form porous spherical nanoassemblies in mixed aqueous media. We also examined the accessible surface area and pore size of spherical aggregates by carrying out nitrogen adsorption− desorption studies48 of HPB derivatives 5 at 295 K. The Brunauer−Emmett−Teller (BET) studies show the presence of pores having size of 1.3 nm, BET surface area 24.18 m2/g and pore volume 0.16 cm3/g, which confirms the intrinsic micro porosity generated within the aggregates (Figure S10 and Table S7).49−52 2.5. Mechanism of Formation of Porous Spherical Nanoassemblies of Derivative 5 in Mixed Aqueous Media. Derivative 5 is having hydrophobic core and hydrophilic methoxy groups at the periphery and concentration dependent 1HNMR studies of the compound suggest the presence of intermolecular π−π stacking between molecules of HPB derivative. We proposed that derivative 5 underwent selfassembly in mixed aqueous media to form porous spherical nanoassemblies via various noncovalent interactions such as aromatic π−π stacking, hydrogen bonding and hydrophobic interactions as shown in Scheme 2. Further, on evaporation of solvent porous spherical assemblies are generated. E

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Figure 6. (A) Fluorescence spectra of derivative 5 showing a ratiometric response in the presence of triethylamine (Et3N) in H2O/THF (8:2, v/v) media (buffered with HEPES, pH 7.05), λex = 372 nm; Inset of A shows fluorescence change (i) orange before and (ii) blue after addition of Et3N. (B) Change in fluorescence intensity upon addition of triethylamine (26 equiv.) to derivative 5.

quenching response (98%) toward aromatic amines having electron donating substituents like p-toluidine, 3,4-dimethoxyaniline, 3,4-dimethylaniline, 2-aminothiophenol, o-phenylenediamine, p-phenylenediamine and N,N-dimethylaniline which indicates more pronounced electron transfer (due to high lying HOMO) due to strong interactions between electron-donor aromatic-amine and electron-acceptor cyano moieties in closely packed aggregates (Figure S14). On the other hand, aromatic amines bearing electron withdrawing substituents such as p-nitroaniline, p-bromoaniline, m-chloroaniline exhibit quenching response to lesser extent (93%) (Figure S14). The detection limit of compounds 5 for aniline was found to be 1.85 nM (Figure S15), respectively which is better than the detection limit reported in the literature for other chemosensors (Table S2). The emission changes in the presence of aromatic amines were totally reversible in the presence of acetic acid and this reversibility cycle was repeated six times (Figure S16). Interestingly, upon addition of tertiary aliphatic amines such as trimethylamine (26 equiv.) to the H2O/THF (8:2, v/v) solution of derivatives 5, emission intensity at 550 nm decreased along with the appearance of a new band at 450 nm which resembles with ICT emission band of molecular state (Figure 6). A 6-fold (I450/I550) emission enhancement was observed at 450 nm (Φ = 0.54) by considering the changes in fluorescence intensity at 450 and 550 nm accompanied by color change from orange to blue (Figure 6A, inset). The detection limit of compound 5 for triethylamine was found to be 19.9 nM (Figure S17). Further, the emission changes in the presence of aliphatic amines were totally reversible in the presence of trifluoroacetic acid and this reversibility cycle was repeated four times (Figure S18). The recognition ability of the aggregates of derivative 5 was also examined toward secondary and primary aliphatic amines. In the presence of diethylamine and dimethylamine, the new blue-shifted emission band appeared at 460 nm, whereas in the case of primary aliphatic amines like ethylamine, propylamine, butylamine, hexylamine, dodecylamine, and cyclohexylamine, the band appeared at 500 nm (Figure S19). Though supramolecular aggregates of derivative 5 exhibit similar ratiometric response toward tertiary/secondary/primary amines but the position of new band differed in all the three categories of amines. This type of behavior can be explained by the Hbonding ability of the amines toward C−H bonds, which

to 5 times. The above results clearly suggest that derivative 5 exhibits stimuli-responsive (pressure/heating) fluorescence transitions in the solid state. 2.7. Molecular Recognition Behavior toward Aliphatic and Aromatic Amines. To date, few supramolecular aggregates are utilized for detection of organic amines, but they suffer from low detection limit and low sensitivity in aqueous media.16,27 Thus, in present investigation, the porous morphology and presence of electron deficient units in highly fluorescent assemblies of derivative 5 prompted us to investigate its sensing applications toward aliphatic and aromatic amines. Upon addition of aromatic amines such as aniline (9.0 equiv.) to the solution of supramolecular aggregates of derivatives 5 in H2O/THF (8:2, v/v) solvent mixture, quenching of the emission band at 550 nm (95%) was observed (Figure 5). The quenching in emission intensity is almost linear obtained at low concentration of aniline (7 equiv./35 μM) in case of compound 5 with Stern−Volmer constant of 1 × 105 M−1 (Figure S11). To get insight into the mechanism, we carried out 1H NMR studies of derivative 5 in the presence of aniline in CDCl3. Upon addition of 9.0 equiv. of aniline to the solution of derivative 5, an average upfield shift of 0.06 ppm was observed in all the aromatic protons (Figure S12), whereas the position of protons of methoxy groups remained unchanged, which suggests π−π stacking between the donor aromatic amine and acceptor cyano groups of derivative 5. We also carried out 13C NMR studies of derivative 5 in the presence of aniline which showed small upfield shift of aromatic carbons and nitrile carbons, no new peak was observed, which again support the electron transfer interactions between the host molecule 5 and guest aniline molecules (Figure S13A). Further, the FT-IR spectra of derivative 5 in the presence of aniline showed the shift of peak from 2218 to 2226 cm−1 (corresponding to nitrile groups) which suggests the electron transfer from aniline to acceptor fumaronitrile core of derivative 5 (Figure S13B). Derivative 5 has low lying HOMO energy level (−5.66 eV), thus, the fluorescence of the aggregates can be quenched efficiently by aromatic amines due to photoinduced electron transfer from the HOMO (for aniline HOMO = −5.63 eV)27 of the aromatic amines to the HOMO of the aggregates of 5. Further, the aggregates of derivative 5 show more pronounced F

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Figure 7. TEM images of (A) untreated, (B) triethylamine (TEA)-treated, and (C) aniline (AN)-treated compound 5 in H2O/THF (8:2, v/v).

On the other hand, PXRD analysis of sample obtained by evaporating solution of 5 (10 mM) in the presence of triethylamine in H2O/THF (8:2) solvent mixture at room temperature showed the appearance of broad peaks at 2θ = 8.5, 15.2, 17.6, 28.5, and 36.9 with d-spacing 10.39, 5.82, 5.03, 3.12, and 2.43 Å, thus, indicating deaggregation of the aggregates (Figure 8, red line marked by stars). These results clearly suggest that aliphatic amines disrupt the H- bonding within the aggregates of derivative 5, which results in deaggregation of larger aggregates. On the other hand, the TEM image of derivative 5 in H2O/ THF (8:2, v/v) in the presence of aniline shows the presence of bigger aggregates having average diameter around 450 nm (Figure 7C) as indicated by the DLS analysis (Figure S22B) and the PXRD pattern of derivative 5 in the presence of aniline almost remained unchanged (Figure 8, blue line). All these results indicate the formation of closely packed aggregates in the presence of aniline. The proposed molecular assembly and sensing mechanism of the aggregates of derivative 5 toward triethylamine and aniline is depicted in Scheme 3. Further, the aggregates of derivative 5 can also detect aliphatic and aromatic amines in groundwater spiked with the solution of triethylamine and aniline (Figure S23). To understand the role of methoxy groups in enhancing the interactions between the aggregates of derivative 5 and triethylamine, we prepared HPB derivative 6 as a model compound (Figures S43−S46). The Diels−Alder reaction of 3 with tetraphenylcyclopenta-2,4-dienone 4b furnished the target compound 6 in 55% yield (Scheme 4). Derivative 6 was found to be AIEE active and also showed solvatochromic and piezochromic behavior (Figures S24−S26). Further, the SEM, TEM, SAXS and DLS studies of derivative 6 in mixed aqueous media clearly indicate the formation of spherical supramolecular aggregates (Figure S27). We also investigated the sensing behavior of aggregates of derivative 6 toward aromatic/aliphatic amines using fluorescence spectroscopy. The fluorescence spectra of derivative 6 in H2O/THF (8:2, v/v) showed complete quenching of emission in the presence of aniline (10 equiv.) (Figure S28). The value of Stern−Volmer constant was found to be 0.64 × 105 M−1 (Figure S29) and a detection limit of derivative 6 was calculated 9.6 nM for aniline (Figure S30). Interestingly, aggregates of derivative 6 showed fluorescence quenching in the presence of aromatic amines (aniline, p-toluidine, 3,4-dimethoxyaniline, 3,4dimethylaniline, 2-aminothiophenol, o-phenylenediamine, pphenylenediamine, N,N-dimethylaniline, p-nitroaniline, p-bromoaniline, m-chloroaniline), whereas no significant change in the emission behavior of derivative 6 was observed in the presence of aliphatic amines (triethylamine, diethylamine, dimethylamine, ethylamine, propylamine, butylamine, hexylamine, dodecylamine, cyclohexylamine) (Figure S31). These

decreases from tertiary to secondary and to primary aliphatic amines. Primary and secondary amines are involved in intermolecular association through hydrogen bonding between nitrogen of one and hydrogen of another molecule, whereas tertiary amines have no intermolecular association. Because of stronger hydrogen bonding ability, tertiary amines interact with the methoxy groups of supramolecular assemblies and hence results in deaggregation of assemblies. The above results suggest that a single probe 5 can differentiate between tertiary/ secondary/primary aliphatic amine and aromatic amine. The 1 H NMR studies of derivative 5 in CDCl3 in the presence of triethylamine show the downfield shift of methoxy C−H protons (Δ = 0.12 ppm) which supports the formation of a Hbonded adduct. Further, a small downfield shift (Δ = 0.03 ppm) was observed in case of other aromatic protons which suggests the disruption of aggregated state of derivative 5 in the presence of triethylamine (Figure S20). Further, the FT-IR spectra of derivative 5 in the presence of triethylamine show the shifting of methoxy C−O bonds from 1246, 1030 to 1230, 1020 cm−1 and shifting of methoxy C−H bonds from 2932 to 2924 cm−1 which again supports the H-bonding interactions between methoxy groups and triethylamine (Figure S21). The TEM image of derivative 5 in H2O/THF (8:2, v/v) clearly suggests the deaggregation of larger aggregates in the presence of triethylamine (Figure 7A, B). The presence of random aggregates of 100 nm was also supported by the DLS analysis (Figure S22A). The solid sample of 5 in absence of triethylamine exhibits sharp peaks mainly located at 2θ = 9.1, 15.9, 18.8, 29.6, 31.5, and 37.6 with d-spacing 9.7, 5.56, 4.71, 3.01, 2.83, and 2.39 Å (Figure 8, black line).

Figure 8. PXRD pattern of (black line) untreated, (blue line) anilinetreated, and (red line) triethylamine-treated compound 5. G

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Scheme 3. Probable Sensing Mechanism of Porous Spherical Nanoassemblies Derivative 5 in H2O/THF (8:2, v/v) toward Triethylamine and Aniline

v/v) to the vapors of triethylamine for 10 min, blue shifting of emission band from 550 to 480 nm was observed. On the other hand, 72% fluorescence quenching of emission of the solution of derivative 5 in H2O/THF (8:2, v/v) was observed upon its exposure to the vapors of aniline for 10 min (Figure S32). We believe that in case of supramolecular aggregates of derivative 5, amine vapors enter into the pores of the aggregates of derivative 5, get absorbed and interact with the molecules, resulting in pronounced sensitivity. We also carried out fluorescence studies of derivative 5 in THF toward aliphatic amines. Only 18% emission enhancement was observed which suggests the weak interactions between derivative 5 and aliphatic amines in molecular state (Figure S33). However, upon exposure of solution of derivative 5 in THF to amines vapors, no significant change in the emission behavior of derivative 5 was observed. Furthermore, the PXRD analysis of the sample obtained by slowly evaporating the THF solution of derivative of 5 having triethylamine showed slight change from the PXRD pattern of derivative 5. (Figure S34). All these studies emphasize the importance of porous morphology of aggregates of derivative 5 for sensing event. In the next section of our discussion, we explored the potential utilization of these aggregates for the preparation of low cost, portable sensing device for the detection of aromatic and aliphatic amines. For this reason, we decorated Whatman

Scheme 4. Synthesis of HPB Derivative 6

studies highlight the role of methoxy groups in derivative 5 for discrimination of aliphatic and aromatic amines. The porous nature of aggregates of derivative 5 prompted us to investigate their sensing ability as fluorescent materials for detection of aliphatic and aromatic amines in vapor phase. Upon exposing the solution of derivative 5 in H2O/THF (8:2,

Figure 9. Images showing the fluorescence change of compound 5 coated paper strips in response to triethylamine (1 × 10−3 M) and aniline (1 × 10−3 M) spray by writing TEA and AN, respectively (under 365 nm UV light). H

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Figure 10. (a−e) Paper strips of 5 showing the variation in fluorescence on the spotted areas after addition of aqueous solution of triethylamine at different concentrations under 365 nm UV light.

Figure 11. (a−g) Paper strips of 5 showing the fluorescence quenching on the spotted areas after addition of aniline in aqueous medium at different concentrations of aniline under 365 nm UV light.

Figure 12. Fluorescence response of thin film of derivative 5 upon exposure of (A, B) aniline for 1 min and (C, D) triethylamine for 5 min (under 365 nm UV light).

aliphatic amines. The derivative 5 coated thin film was exposed to the environment of aniline vapor in a closed flask; the fluorescence intensity was quenched within 1 min (Figure 12A, B). On the other hand, upon exposing derivative 5 coated thin film to the vapors of triethylamine for 5 min, change in emission color from orange to green was observed (Figure 12C, D). Interestingly, when these films are exposed to air for next 30 s, initial orange fluorescence of thin films were revived, thus, indicating an instant reversibility of the response toward amine vapors. These results clearly indicate that derivative 5-coated thin films can be utilized for the discrimination of aliphatic and aromatic amines in vapor phase with excellent reversibility.

filter paper strips by dip-coating the solution of derivative 5 and dried under vacuum. The aqueous solutions of triethylamine and aniline (10−3 M) were sprayed separately onto the strips by writing “TEA” and ‘AN′, respectively and the solvent was evaporated in air. A blue fluorescent “TEA” and nonfluorescent “AN” images appeared on the regions exposed to triethylamine and aniline, respectively (Figure 9). For erasing, the strips were washed with water/treated with dilute acid and the orange fluorescence was revived in the amine-exposed areas that indicate the reversibility of the recognition event. Next, we performed the paper strip test by treating with different concentrations of triethylamine to show blue fluorescent spots and this showed the interesting behavior of 5 is essential for the detection of triethylamine until the limit of 1 × 10−6 M (Figure 10). The detection limit of ∼1.01 ng/cm2 was obtained by spotted 10 μL volume of 1 μM triethylamine solution on the filter paper strips covering 1 cm2 area. We also performed the paper strip test for trace detection of aniline by treating with different concentrations of aniline solution up to 1 × 10−8 M level (Figure 11). In case of aniline, a detection limit of ∼9.3 pg/cm2 was obtained by spotted 10 μL volume of 1 × 10−8 M aniline. These results clearly suggest that aggregates of derivative 5 can detect triethylamine and aniline at very low concentration in aqueous sample, which makes dip strips of derivative 5 a powerful tool for the detection of triethylamine and aniline in aqueous media. Further, we investigated the sensing applications of thin films of derivative 5 for the detection of vapors of aromatic and

3. CONCLUSIONS In summary, D−A−D-based derivative 5 with fumaronitrile scaffold as acceptor and methoxy units as a donor have been designed and synthesized. Derivative 5 exhibits good solid state luminescence and shows reversible piezo- and thermochromism in solid state. Because of its AIEE characteristics, derivative 5 formed porous spherical nanoassemblies in H2O/ THF (8:2, v/v) media. These fluorescent aggregates have been utilized for the selective detection of organic amines in solution and in vapor phase. Interestingly, porous aggregates of derivative 5 show ratiometric response toward primary amines and “turn-off” response toward aromatic amines. In addition, the compound 5 coated fluorescent paper strips were utilized for the sensitive detection of triethylamine and aniline in I

DOI: 10.1021/acsami.7b09791 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX

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ACS Applied Materials & Interfaces aqueous media by writing “TEA” and “AN”. The ∼1.01 ng/cm2 and 9.3 pg/cm2 detection level was achieved for triethylamine and aniline, respectively, by using a portable paper-based test strip assay, affording a simple method for prompt discrimination of aliphatic and aromatic amines in solution and in vapor phase.

4H), 7.38 (t, J = 7.5 Hz, 6H), 7.00 (d, J = 10 Hz, 4H), 6.93−6.80 (m, 42H); 13C NMR (100 MHz, CDCl3, ppm): δ = 140.6, 140.2, 140.0, 135.8, 134.9, 132.5, 132.1, 131.8, 131.3, 130.1, 126.9, 126.6, 125.7, 125.4, 120.1, 118.9; ESI-MS (m/z): 1143.4657 [M + H]+; FT-IR νmax (cm−1): 2219 (−CN); Elemental anal. Calcd for C88H58N2: C, 92.44; H, 5.11; N, 2.45, Found: C 92.45%; H 5.09%; N 2.46%.

4. EXPERIMENTAL SECTION

S Supporting Information *

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4.1. General Experimental Methods and Materials.59 The general experimental methods, quantum yield calculations and materials used are same as reported earlier by us.59 Brunauer− Emmett−Teller (BET) surface area and SAXS pattern are measured by Brunauer−Emmett−Teller (BET) surface area analyzer and Xeuss SAXS instrument (model C HP 100 fm), respectively. 4.2. UV−Vis and Fluorescence Titrations.59 In each UV−vis and fluorescence titration, 3 mL of 5 μM solution of derivative 5/6 in H2O/THF (8:2, v/v) media were taken in a 3 mL cuvette prepared from 1 × 10−1 M standard solution. Aliquots of freshly prepared standard solutions (1 × 10−1 to 1 × 10−3 M) of aliphatic amines (triethylamine, diethylamine, dimethylamine, ethylamine, propylamine, butylamine, hexylamine, dodecylamine, cyclohexylamine) and aromatic amines (aniline, p-toluidine, 3,4-dimethoxyaniline, 3,4dimethylaniline, 2-aminothiophenol, o-phenylenediamine, p-phenylenediamine, N,N-dimethylaniline, p-nitroaniline, p-bromoaniline, mchloroaniline) in THF were used for UV−vis and fluorescence titrations. 4.3. Experimental Details of Sensing of Organic Amines at Vapor Phase.60 Two glass vials containing 3 mL of solution of aggregates of derivative 5 were inserted separately in two bigger glass vials filled with 1.0 mL of aliphatic (triethylamine) and aromatic amines (aniline). The vials were sealed with caps to make saturate inside vial with vapors of aromatic/aliphatic amines. Fluorescent spectra were then recorded at different time intervals. 4.4. Preparation of Test Strips. Filter paper test strips (5 cm × 2 cm) were prepared by dip-coating the compound 5 (1 mM) followed by dried under vacuum. Another paper strip (6 cm × 6 cm) was cut into pieces (1 cm × 1 cm) which were then used for trace detection of organic amines at various concentrations. 4.5. Synthesis of 2,3-Bis(3′,4′-bis(4-methoxyphenyl)-5′,6′diphenyl-[1,1′:2′,1″-terphenyl]-4-yl)fumaronitrile (5). Compound 3 (0.43 g, 1.0 mmol) and compound 4a (0.89 g, 2.0 mmol) were mixed in diphenyl ether in two necked RBF and degassed three times followed by refluxing at 240 °C for 48 h under nitrogen atmosphere. The reaction mixture was then cooled to room temperature followed by addition of methanol. A yellow-colored solid separated out which was filtered and was purified by column chromatography (eluent, hexane:chloroform, 1:4) to furnish yellow solid in 50% yield (0.63 g) (Figures S39−S42). 1H NMR (400 MHz, CDCl3, ppm): δ = 7.76 (d, J = 4 Hz, 1H), 7.64 (d, J = 8 Hz, 1H), 7.57 (d, J = 4 Hz, 2H), 7.47 (d, J = 8 Hz, 1H), 7.40−7.33 (m, 6H), 7.22 (d, J = 8 Hz, 2H), 7.12 (t, J = 6 Hz, 2H), 7.04 (d, J = 8 Hz, 2H), 6.96− 6.80 (m, 24H), 6.73 (d, J = 8 Hz, 6H), 6.64 (t, J = 6 Hz, 2H), 6.51 (d, J = 4 Hz, 1H), 6.45 (d, J = 4 Hz, 4H), 3.65 (s, 12H, -OMe). 13C NMR (100 MHz, CDCl3, ppm): δ = 141.0, 139.5, 137.2, 135.3, 132.8, 132.5, 131.6, 131.3, 131.1, 130.7, 130.1, 129.7, 128.5, 127.0, 120.6, 118.8, 114.9, 56.2; ESI-MS (m/z): 1285.4919 [M + Na]+; FT-IR νmax (cm−1): 2932 (C−H in CH3), 2218 (−CN), 1246, 1030 (O−CH3). Elemental anal. Calcd for C92H66N2O4: C, 87.45; H, 5.27; N, 2.22, Found: C 87.46%; H 5.28%; N 2.20%. 4.6. Synthesis of 2,3-Bis(3′,4′,5′,6′-diphenyl-[1,1′:2′,1″-terphenyl]-4-yl)fumaronitrile (6). Compound 3 (0.43 g, 1.0 mmol) and compound 4b (0.77 g, 2.0 mmol) were mixed in diphenyl ether in two-necked RBF and degassed three times followed by refluxing at 240 °C for 48 h under a nitrogen atmosphere. The reaction mixture was then cooled to room temperature followed by addition of methanol. A green colored solid separated out that was purified by column chromatography using hexane:chloroform (1:2) as eluent to get light green solid in 55% yield (0.63 g) (Figures S43−46). 1H NMR (500 MHz, CDCl3, ppm): δ = 7.73 (d, J = 10 Hz, 2H), 7.60 (dd, J = 10 Hz,

ASSOCIATED CONTENT

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsami.7b09791. 1 H, 13C, mass spectra, and IR spectrum of compounds 3, 5, and 6; UV−vis and fluorescence studies; cyclic voltammogram, time-resolved decay profile, detection limits; confocal, SEM, TEM images; SAXS pattern, DLS studies, BET data, FT-IR, and table of comparison of present manuscript with previous reports (PDF)

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. ORCID

Manoj Kumar: 0000-0002-8740-1928 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS M.K. is thankful to SERB (ref no. EMR/2016/003473). S.P. is thankful to UGC (New Delhi) for Senior Research Fellowship (SRF). We are also thankful to UGC (New Delhi) for “University with Potential for Excellence” (UPE) project. This article is dedicated to Dr. Harjit Singh (Prof. Emeritus) on his 80th birthday.

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REFERENCES

(1) Gao, T.; Tillman, E. S.; Lewis, N. S. Detection and Classification of Volatile Organic Amines and Carboxylic Acids Using Arrays of Carbon Black-Dendrimer Composite Vapor Detectors. Chem. Mater. 2005, 17, 2904−2911. (2) Akceylan, E.; Bahadir, M.; Yılmaz, M. Removal Efficiency of a Calix[4]arene-based Polymer for Water-soluble Carcinogenic Direct Azo Dyes and Aromatic Amines. J. Hazard. Mater. 2009, 162, 960− 966. (3) Lawrence, S. A.; Amines: Synthesis, Properties and Applications; Cambridge University Press: Cambridge, U.K., 2004. (4) Timmer, B.; Olthuis, W.; Berg, A. V. D. Ammonia Sensors and Their Applications-a Review. Sens. Actuators, B 2005, 107, 666−677. (5) Triethylamine [MAK Value Documentation, 1999]. The MAK Collection for Occupational Health and Safety; Wiley: New York, 2012; Vol. 13, pp 267−280. (6) Ellis, D. L.; Zakin, M. R.; Bernstein, L. S.; Rubner, M. F. Conductive Polymer Films as Ultrasensitive Chemical Sensors for Hydrazine and Monomethylhydrazine Vapor. Anal. Chem. 1996, 68, 817−822. (7) Zelnick, S. D.; Mattie, D. R.; Stepaniak, P. C. Occupational Exposure to Hydrazines: Treatment of Acute Central Nervous System Toxicity. Aviat. Space Environ. Med. 2003, 74, 1285−1291. (8) Vineis, P.; Pirastu, R. Aromatic Amines and Cancer. Cancer, Causes Control, Pap. Symp. 1997, 8, 346−355. (9) Salazar, M. T.; Smith, T. K.; Harris, A. High-Performance Liquid Chromatographic Method for Determination of Biogenic Amines in Feedstuffs, Complete Feeds, and Animal Tissues. J. Agric. Food Chem. 2000, 48, 1708−1712. J

DOI: 10.1021/acsami.7b09791 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX

Forum Article

ACS Applied Materials & Interfaces (10) Stillwell, W.; Bryant, M. S.; Wishnok, J. S. GC/MS Analysis of Biologically Important Aromatic Amines. Application to Human Dosimetry. Biomed. Environ. Mass Spectrom. 1987, 14, 221−227. (11) Zhang, Y.; Peng, C.; Ma, X.; Che, Y.; Zhao, J. Fluorescent and Photoconductive Nanoribbons as a Dual-mode Sensor for Selective Discrimination of Alkyl Amines versus Aromatic Amines. Chem. Commun. 2015, 51, 15004−15007. (12) Rakow, N. A.; Sen, A.; Janzen, M. C.; Ponder, J. B.; Suslick, K. S. Molecular Recognition and Discrimination of Amines with a Colorimetric Array. Angew. Chem., Int. Ed. 2005, 44, 4528−4532. (13) Feuster, E. K.; Glass, T. E. Detection of Amines and Unprotected Amino Acids in Aqueous Conditions by Formation of Highly Fluorescent Iminium Ions. J. Am. Chem. Soc. 2003, 125, 16174−16175. (14) Longstreet, A. R.; Jo, M.; Chandler, R. R.; Hanson, K.; Zhan, N.; Hrudka, J. J.; Mattoussi, H.; Shatruk, M.; McQuade, D. T. Ylidenemalononitrile Enamines as Fluorescent “Turn-On” Indicators for Primary Amines. J. Am. Chem. Soc. 2014, 136, 15493−15496. (15) McGrier, P. L.; Solntsev, K. M.; Miao, S.; Tolbert, L. M.; Miranda, O. R.; Rotello, V. M.; Bunz, U. H. F. Hydroxycruciforms: Amine-Responsive Fluorophores. Chem. - Eur. J. 2008, 14, 4503−4510. (16) Shi, L.; Fu, Y.; He, C.; Zhu, D.; Gao, Y.; Wang, Y.; He, Q.; Cao, H.; Cheng, J. A Mild and Catalyst-free Conversion of Solid Phase Benzylidenemalononitrile/Benzylidenemalonate to N-benzylideneAmine and Its Application for Fluorescence Detection of Primary Alkyl Amine Vapor. Chem. Commun. 2014, 50, 872−874. (17) Rochat, S.; Swager, T. M. Fluorescence Sensing of Amine Vapors Using a Cationic Conjugated Polymer Combined with Various Anions. Angew. Chem., Int. Ed. 2014, 53, 9792−9796. (18) Che, Y.; Yang, X.; Loser, S.; Zang, L. Expedient Vapor Probing of Organic Amines Using Fluorescent Nanofibers Fabricated from an n-Type Organic Semiconductor. Nano Lett. 2008, 8, 2219−2223. (19) Mallick, A.; Garai, B.; Addicoat, M. A.; St. Petkov, P.; Heine, T.; Banerjee, R. Solid State Organic Amine Detection in a Photochromic Porous Metal Organic Framework. Chem. Sci. 2015, 6, 1420−1425. (20) Feng, H.-J.; Xu, L.; Liu, B.; Jiao, H. Europium Metal−organic Frameworks as Recyclable and Selective Turn-off Fluorescent Sensors for Aniline Detection. Dalton Trans. 2016, 45, 17392−17400. (21) Han, T.; Lam, J. W.; Zhao, N.; Gao, M.; Yang, Z.; Zhao, E.; Dong, Y.; Tang, B. Z. A Fluorescence-Switchable Luminogen in The Solid State: A Sensitive and Selective Sensor for The Fast “Turn-On” Detection of Primary Amine Gas. Chem. Commun. 2013, 49, 4848− 4850. (22) Gao, M.; Li, S.; Lin, Y.; Geng, Y.; Ling, X.; Wang; Qin, A. L.; Tang, B. Z. Fluorescent Light-Up Detection of Amine Vapors Based on Aggregation-Induced Emission. ACS Sens. 2016, 1, 179−184. (23) Nakamura, M.; Sanji, T.; Tanaka, M. Fluorometric Sensing of Biogenic Amines With Aggregation-Induced Emission-Active Tetraphenylethenes. Chem. - Eur. J. 2011, 17, 5344−5349. (24) Zhang, Y.; Peng, C.; Ma, X.; Che, Y.; Zhao, J. Fluorescent and Photoconductive Nanoribbons as a Dual-mode Sensor for Selective Discrimination of Alkyl Amines versus Aromatic Amines. Chem. Commun. 2015, 51, 15004−15007. (25) Pang, X.; Yu, X.; Lan, H.; Ge, X.; Li, Y.; Zhen, X.; Yi, T. Visual Recognition of Aliphatic and Aromatic Amines Using a Fluorescent Gel: Application of a Sonication-Triggered Organogel. ACS Appl. Mater. Interfaces 2015, 7, 13569−13577. (26) Wang, S.; Xue, P.; Wang, P.; Yao, B. Emission Enhanced TwoComponent Gels for The Detection of Organic Amine Vapors. New J. Chem. 2015, 39, 6874−6881. (27) Xue, P.; Xu, Q.; Gong, P.; Qian, C.; Ren, A.; Zhang, Y.; Lu, R. Fibrous Film of a Two-Component Organogel as a Sensor to Detect and Discriminate Organic Amines. Chem. Commun. 2013, 49, 5838− 5840. (28) Rakow, N. A.; Sen, A.; Janzen, M. C.; Ponder, J. B.; Suslick, K. S. Molecular Recognition and Discrimination of Amines with a Colorimetric Array. Angew. Chem. 2005, 117, 4604−4608. (29) Bhalla, V.; Pramanik, S.; Kumar, M. Hexaphenylbenzene-based Fluorescent Aggregates for Detection of Zinc and Pyrophosphate Ions

in Aqueous Media: Tunable Self-assembly Behaviour and Construction of a Logic Device. New J. Chem. 2017, 41, 4806−4813. (30) Bhalla, V.; Pramanik, S.; Kumar, M. Cyanide Modulated Fluorescent Supramolecular Assembly of a Hexaphenylbenzene Derivative for Detection of Trinitrotoluene at the Attogram Level. Chem. Commun. 2013, 49, 895−897. (31) Kumar, M.; Vij, V.; Bhalla, V. Vapor-Phase Detection of Trinitrotoluene by AIEE-Active Hetero-oligophenylene-Based Carbazole Derivatives. Langmuir 2012, 28, 12417−12421. (32) Pramanik, S.; Bhalla, V.; Kim, H. M.; Singh, H.; Lee, H. W.; Kumar, M. A Hexaphenylbenzene Based AIEE Active Two Photon Probe for the Detection of Hydrogen Sulfide with Tunable Selfassembly in Aqueous Media and Application in Live Cell Imaging. Chem. Commun. 2015, 51, 15570−15573. (33) Mei, J.; Leung, N. L. C.; Kwok, R. T. K.; Lam, J. W. Y.; Tang, B. Z. Aggregation-Induced Emission: Together We Shine, United We Soar! Chem. Rev. 2015, 115, 11718−11940. (34) Sandeep, A.; Praveen, V. K.; Kartha, K. K.; Karunakaran, V.; Ajayaghosh, A. Supercoiled Fibres of Self-sorted Donor−Acceptor Stacks: A Turn-off/Turn-on Platform for Sensing Volatile Aromatic Compounds. Chem. Sci. 2016, 7, 4460−4467. (35) Shen, X. Y.; Wang, Y. J.; Zhao, E.; Yuan, W. Z.; Liu, Y.; Lu, P.; Qin, A.; Ma, Y.; Sun, J. Z.; Tang, B. Z. Effects of Substitution with Donor−Acceptor Groups on the Properties of Tetraphenylethene Trimer: Aggregation-Induced Emission, Solvatochromism, and Mechanochromism. J. Phys. Chem. C 2013, 117, 7334−7347. (36) Zhu, Z.; Qian, J.; Zhao, X.; Qin, W.; Hu, R.; Zhang, H.; Li, D.; Xu, Z.; Tang, B. Z.; He, S. Stable and Size-Tunable AggregationInduced Emission Nanoparticles Encapsulated with Nanographene Oxide and Applications in Three-Photon Fluorescence Bioimaging. ACS Nano 2016, 10, 588−597. (37) Yeh, H.-C.; Wu, W.-C.; Wen, Y.-S.; Dai, D.-C.; Wang, J.-K.; Chen, C.-T. Derivative of α,β-Dicyanostilbene: Convenient Precursor for the Synthesis of Diphenylmaleimide Compounds, E−Z Isomerization, Crystal Structure, and Solid-State Fluorescence. J. Org. Chem. 2004, 69, 6455−6462. (38) Kataria, M.; Pramanik, S.; Kaur, N.; Kumar, M.; Bhalla, V. Ferromagnetic α-Fe2O3 NPs: A Potential Catalyst in Sonogashira− Hagihara Cross Coupling and Hetero-Diels-Alder Reactions. Green Chem. 2016, 18, 1495−1505. (39) Thomas, K. R. J.; Velusamy, M.; Lin, J. T.; Chuen, C. H.; Tao, Y. T. Hexaphenylphenylene Dendronised Pyrenylamines for Efficient Organic Light-Emitting Diodes. J. Mater. Chem. 2005, 15, 4453−4459. (40) Pommerehne, J.; Vestweber, H.; Gusss, W.; Mahrt, R. F.; Bassler, H.; Porsch, M.; Daub, J. Efficient Two Layer Leds on a Polymer Blend Basis. Adv. Mater. 1995, 7, 551−554. (41) Zhou, Y.; He, Q. G.; Yang, Y.; Zhong, H. Z.; He, C.; Sang, G. Y.; Liu, W.; Yang, C. H.; Bai, F. L.; Li, Y. F. Binaphthyl-Containing Greenand Red-Emitting Molecules for Solution-Processable Organic LightEmitting Diodes. Adv. Funct. Mater. 2008, 18, 3299−3306. (42) Li, W.; Liu, D.; Shen, F.; Ma, D.; Wang, Z.; Feng, T.; Xu, Y.; Yang, B.; Ma, Y. A Twisting Donor-Acceptor Molecule with an Intercrossed Excited State for Highly Efficient, Deep-Blue Electroluminescence. Adv. Funct. Mater. 2012, 22, 2797−2803. (43) Singh, G.; Bhalla, V.; Kumar, M. Carbazole-Functionalized Polyphenylene-Decorated Solid State Emissive D−A−D Molecules: Reduced Donor−Acceptor Interaction and Enhanced Emission in the Solid State. Phys. Chem. Chem. Phys. 2015, 17, 22079−22089. (44) Xu, D.; Ma, Y.; Jing, Z.; Han, L.; Singh, B.; Feng, J.; Shen, X.; Cao, F.; Oleynikov, P.; Sun, H.; Terasaki, O.; Che, S. π- π Interaction of Aromatic Groups in Amphiphilic Molecules Directing for SingleCrystalline Mesostructured Zeolite Nanosheets. Nat. Commun. 2014, 5, 4262−4270. (45) Sher, P.; Custódio, C. A.; Mano, J. F. Layer-By-Layer Technique for Producing Porous Nanostructured 3D Constructs Using Moldable Freeform Assembly of Spherical Templates. Small 2010, 6, 2644− 2648. (46) Senthilkumar, T.; Asha, S. K. Self-Assembly in Tailor-Made Polyfluorenes: Synergistic Effect of Porous Spherical Morphology and K

DOI: 10.1021/acsami.7b09791 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX

Forum Article

ACS Applied Materials & Interfaces FRET for Visual Sensing of Bilirubin. Macromolecules 2013, 46, 2159− 2171. (47) Wessig, M.; Drescher, M.; Polarz, S. Probing Functional Group Specific Surface Interactions in Porous Solids Using ESR Spectroscopy as a Sensitive and Quantitative Tool. J. Phys. Chem. C 2013, 117, 2805−2816. (48) Thompson, C. M.; McCandless, G. T.; Wijenayake, S. N.; Alfarawati, O.; Jahangiri, M.; Kokash, A.; Tran, Z.; Smaldone, R. A. Substituent Effects on the Gas Sorption and Selectivity Properties of Hexaphenylbenzene and Hexabenzocoronene Based Porous Polymers. Macromolecules 2014, 47, 8645−8652. (49) Tatamitani, Y.; Liu, B.; Shimada, J.; Ogata, T.; Ottaviani, P.; Maris, A.; Caminati, W.; Alonso, J.L. ́ Weak, Improper, C−O···H−C Hydrogen Bonds in the Dimethyl Ether Dimer. J. Am. Chem. Soc. 2002, 124, 2739−2743. (50) Palusiak, M.; Grabowski, S. J. Methoxy Group as an Acceptor of Proton in Hydrogen Bonds. J. Mol. Struct. 2002, 642, 97−104. (51) Tilford, R. W.; Mugavero, S. J.; Pellechia, P. J.; Lavigne, J. Tailoring Microporosity in Covalent Organic Frameworks. Adv. Mater. 2008, 20, 2741−2746. (52) Ghanem, B. S.; Hashem, M.; Harris, K. D. M.; Msayib, K. J.; Xu, M.; Budd, P. M.; Chaukura, N.; Book, D.; Tedds, S.; Walton, A.; McKeown, N. B. Triptycene-Based Polymers of Intrinsic Microporosity: Organic Materials That Can Be Tailored for Gas Adsorption. Macromolecules 2010, 43, 5287−5294. (53) Dou, C.; Chen, D.; Iqbal, J.; Yuan, Y.; Zhang, H.; Wang, Y. Multistimuli-Responsive Benzothiadiazole-Cored Phenylene Vinylene Derivative with Nanoassembly Properties. Langmuir 2011, 27, 6323− 6329. (54) Sagara, Y.; Mutai, T.; Yoshikawa, I.; Araki, K. Material Design for Piezochromic Luminescence: Hydrogen-Bond-Directed Assemblies of a Pyrene Derivative. J. Am. Chem. Soc. 2007, 129, 1520−1521. (55) Ito, H.; Saito, T.; Oshima, N.; Kitamura, N.; Ishizaka, S.; Hinatsu, Y.; Wakeshima, M.; Kato, M.; Tsuge, K.; Sawamura, M. Reversible Mechanochromic Luminescence of [(C6F5Au)2(μ-1,4Diisocyanobenzene)]. J. Am. Chem. Soc. 2008, 130, 10044−10045. (56) Dou, C.; Chen, D.; Iqbal, J.; Yuan, Y.; Zhang, H.; Wang, Y. Multistimuli-Responsive Benzothiadiazole-Cored Phenylene Vinylene Derivative with Nanoassembly Properties. Langmuir 2011, 27, 6323− 6329. (57) Zhang, H.; Zhang, Z.; Ye, K.; Zhang, J.; Wang, Y. Organic Crystals with Tunable Emission Colors Based on a Single Organic Molecule and Different Molecular Packing Structures. Adv. Mater. 2006, 18, 2369−2372. (58) Jenekhe, S.; Osaheni, J. Excimers and Exciplexes of Conjugated Polymers. Science 1994, 265, 765−768. (59) Pramanik, S.; Bhalla, V.; Kumar, M. Hexaphenylbenzene-Based Fluorescent Aggregates for Ratiometric Detection of Cyanide Ions at Nanomolar Level: Set-Reset Memorized Sequential Logic Device. ACS Appl. Mater. Interfaces 2014, 6, 5930−5939. (60) Pramanik, S. Supramolecular Aggregates of AIEE Active Hexaphenylbenzene based Molecules: A Search for New Functional Nanomaterials. Ph. D Thesis, Guru Nanak Dev University, Amritsar, India, 2017.

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