Gold nanoparticles immobilized polymeric PBI derivative: Productive

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Gold nanoparticles immobilized polymeric PBI derivative: Productive, portable and photocatalytic system for Heck coupling Meenal Kataria, Manoj Kumar, Zujhar Singh, and Vandana Bhalla ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b00031 • Publication Date (Web): 25 May 2018 Downloaded from http://pubs.acs.org on May 25, 2018

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ACS Sustainable Chemistry & Engineering

Gold nanoparticles immobilized polymeric PBI derivative: Productive, portable and photocatalytic system for Heck coupling. Meenal Kataria, Manoj Kumar, Zujhar Singh and Vandana Bhalla* E-mail: [email protected]

Department of Chemistry, UGC Sponsored Centre for Advanced Studies-II Guru Nanak Dev University, Amritsar 143005, Punjab, KEYWORDS: J-aggregates, Supramolecular ensemble, Green Synthesis, Multifold Heck Coupling, Dip catalytic strip.

ABSTRACT Perylene bisimide (PBI) derivative 3 having thiophene moieties at the bay positions has been designed and synthesized which forms J-aggregates in aqueous media and these aggregates serve as reactors for the generation of Au NPs and themselves undergo oxidative polymerization through thiophene moieties to generate polymeric species 4. The as prepared polymeric species 4 and gold NPs generated supramolecular ensemble 4: Au NPs which serve as promising photocatalytic system for Heck and multifold Heck coupling reaction. Moreover, the work being reported in this manuscript demonstrates the deposition of supramolecular ensemble 1 ACS Paragon Plus Environment

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4: Au NPs on paper strips for preparation of “dip catalytic strip” as an efficient, economic, efficient, green, portable and recyclable catalytic system. The efficiency of this catalytic system is evident from its broad scope, benign reaction conditions, multifold Heck coupling, seven times reusability (in solution form) and eight times reusability (“dip catalytic strip”).

INTRODUCTION Palladium catalysed Heck coupling1-4 is one of the most powerful protocols for the olefination of aryl/vinyl halides for the preparation of a variety of complex compounds having medicinal, industrial and material applications.5-7 The conventional Heck reaction is catalysed by palladium based homogeneous catalytic systems under thermal and inert conditions.8-11 Although palladium based catalytic systems are efficient but low thermal stability and almost no reusability of these systems are big disadvantages of this strategy. To make the catalytic system more viable and economic several palladium based heterogeneous catalytic systems have been developed. Heterogeneous catalysis could successfully resolve the issues related with recyclability, however, reaction protocols still suffered from limitations such as requirement of inert conditions and use of organic solvent as the reaction media.12,13 Thus, the development of an efficient catalytic system for Heck reaction which could overcome all the above limitations is highly desired. Our research area is emphasized around generation of reactors based on assemblies of small molecules which serve as reducing and stabilizing agents for the generation of metal NPs. As prepared metal nanoparticles in combination with supramolecular assemblies are utilized as catalytic/photocatalytic systems for carrying out various organic transformations under benign and eco-friendly conditions.14-16

In continuation of our efforts in this direction, we were

concerned in generation of an efficient catalytic system for performing Heck coupling reaction under eco-friendly conditions. We envisioned that by switching thermal heating with visible 2 ACS Paragon Plus Environment

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radiation, stability, recyclability and the environmental advantages of the catalytic system could be improved.17 Recently, several palladium based photocatalytic systems have been reported for carrying out Heck reaction under mild conditions.18,19 However, these catalytic systems work efficiently only under inert atmosphere and in the presence of organic solvent as reaction media. Above all, the reaction protocols still require thermal heating at 40˚C.18 We hypothesized that by using plasmonic metal based catalytic system instead of palladium based systems these limitations could be removed. Very recently, a dinuclear gold complex has been reported as an proficient photocatalyst for performing Heck coupling.20 To furnish desired product in higher amount, reaction conditions necessitates the presence of organic solvent and longer reaction time (30-36h). Furthermore, the recyclability of catalyst was never explored. This report inspired us to develop a gold based recyclable photo-catalytic system for carrying out Heck coupling reaction. Recently, we reported polythiophene encapsulated bimetallic Au-Fe3O4 nano-hybrid materials (Figure S1 in the Supporting Information) a photocatalytic system for performing C-H activation of unactivated anilines.21 As a test of our hypothesis, we carried out the reaction between iodobenzene and 4-vinylpyridine under photocatalytic conditions using this catalytic system in aqueous media. The target product was attained in 68% yield after 5h (vide infra). Encouraged by these results, we planned to modify the existing photocatalytic system. We envisioned that light harvesting in visible region may be more facilitated by using assemblies based on organic dye and hence efficiency of the catalytic system may be enhanced.22-24 Thus, we designed and synthesized PBI derivative 3 having thiophene moieties.25-27 We chose Peylene bisimide (PBI) moiety as the dye due its absorption in visible region.28,

29

We expected that presence of

thiophene groups will enhance the binding ability of probe towards gold ions. In mixed aqueous media PBI moiety 3 formed J-aggregates which served as reactors for the generation of gold 3 ACS Paragon Plus Environment


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nanoparticles. Fortunately, our idea worked and in situ prepared supramolecular ensemble of oxidized assemblies and gold NPs (supramolecular polymer 4: Au NPs) exhibited high photocatalytic activity in Heck coupling reaction under mild and eco-friendly conditions. Thus, work being presented in this manuscript has several advantages. First, PBI derivative 3 having thiophene groups at the bay positions has been synthesized. Derivative 3 undergoes selfassembly in mixed aqueous media to generate J-aggregates. The assembled system showed strong interaction towards gold ions which eventually resulted in the formation of gold ions to gold NPs . This reduction process was accompanied by oxidative polymerization of thiophene groups of the PBI derivative to generate supramolecular ensemble of polythiophene species and gold nanoparticles. This is the first report of gold mediated oxidative polymerization of PBI derivative. Second, aggregates of polythiophene species in combination with Au NPs exhibited high photocatalytic efficiency in Heck reaction under aerial conditions and in mixed aqueous media. This photocatalytic system could be reused upto seven cycles and after seventh cycle the target compound was achieved in 73 % yield. The photocatalytic efficiency of the prepared supramolecular ensemble is better than the other reported catalytic/photocatalytic systems in literature (Table S4, in the Supporting Information). Third, by employing as prepared catalytic system, less reactive aryl chlorides even underwent Heck coupling reaction smoothly. Earlier, there are few reports regarding catalytic systems which make the aryl chlorides reactive, however, the reaction conditions require longer reaction time (upto 48 h) and the target compound was achieved in lower yields.30-32 In this context, the photocatalytic system being reported in this manuscript could activate the aryl chlorides to furnish the target compounds in short time (5-6h) and good yields (57-60%). Fourth, supramolecular polymer 4: Au NPs exhibited high catalytic efficiency in multifold Heck coupling reaction of a variety of substrates. 4 ACS Paragon Plus Environment

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Earlier, palladium based

heterogeneous recyclable catalytic system has been reported for

multifold Heck coupling reaction.33 Fifth, the work being reported in this manuscript demonstrates the utilization of supramolecular polymer 4: Au NPs as portable ―dip catalytic strip‖34,

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in Heck coupling reaction. The portable ―dip catalytic strip‖ has been prepared by

impregnated supramolecular polymer 4: Au NPs on a filter paper strip. Unprecedented, this is the first report which demonstrates the preparation of paper based portable catalytic system for carrying out Heck coupling reaction by deposition of aggregates of polymer of PBI derivative 3 and gold NPs. Scheme 1: Synthesis of perylene based derivative 3.

RESULTS & DISCUSSIONS The Suzuki- Miyura protocol between 136 and boronic ester 2 furnished the compound 3 via in 72% yield (Scheme 1). The structure of the compound was elucidated by various spectroscopic methods (Figure S46 A-C, Supporting Information). The UV-vis. spectrum exhibits derivative 3 in THF showed the absorption bands at 340, 447, 514 and 560 nm, respectively. Upon the addition of water fractions upto 60 % to the THF solution of derivative 3, all the absorption bands were red shifted (Figure S2, Supporting 5 ACS Paragon Plus Environment


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Information). In the fluorescence studies, the two emission bands were observed at 525 (ϕ =0.89) and 563 nm (ϕ =0.35) respectively, upon excitation at 447 nm. The emission band at 525 nm was red shifted to 536 nm upon the addition of aliquots of water fraction upto 60 % to this solution and its emission intensity was reduced (ϕ =0. 37). On the other hand, the emission band at 563 nm was broadened and its emission intensity was drastically reduced in the presence of water as a co-solvent (Figure S3a, Supporting Information). Thus, both absorption and emission studies of derivative 3 suggested the formation of J-type aggregates (Figure S3b, Supporting Information). Further the formation of J-type aggregates of compound 3 were confirmed from the temperature dependent UV-vis. and concentration-dependent 1H NMR studies (Figure S4& S5 in the Supporting Information). The scanning electron microscope (SEM) image showed the presence of disc shaped aggregates of compound 3 in H2O/THF (6 : 4, v/v) solvent mixture (Figure S6, Supporting Information). The Dynamic light scattering (DLS) analysis of the same sample indicated the presence of aggregates having size in the range of 300-700 nm (Figure S7, Supporting Information). Next, we examined the affinity of aggregates of derivative 3 towards Au3+ ions using absorption and fluorescence spectroscopic studies. Upon adding Au3+ ions to the solution of aggregates of derivative 3 (6:4; H2O: THF; v/v), the intensity of all the absorption bands was decreased. Furthermore, after keeping the solution for 30 minutes, a new absorption band corresponding to localised surface plasmon resonance (LSPR) of Au NPs appeared at 570 nm37 (Figure S8, Supporting Information). These studies suggested that the aggregates of derivative 3 act as reactors for the generation of gold NPs in mixed aqueous media and during this event aggregates of derivative 3 were oxidized to form conjugated polymeric structure (vide infra). The UV-vis. studies of derivative 3 in the presence of other metal ions (as Ag+, Cu2+, Fe3+, Hg2+, Co2+, Zn2+, Fe2+, Pb2+, Ni2+, Pd2+, Cd2+, Mg2+, and 6 ACS Paragon Plus Environment

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Ba2+) didn‘t exhibit any change (Figure S9, Supporting Information). In the fluorescence studies, upon adding Au3+ ions (60 equiv.) to the solution of aggregates of derivative 3 (6:4; H2O: THF; v/v), enhancement in the emission band at 536 nm (ϕ =0.85) was observed and the emission band at 571 nm was completely disappeared (Figure S10a, Supporting Information). After keeping the same solution for 30 minutes, the emission spectrum showed the quenching of emission of both the bands (Figure S10b, Supporting Information). We believe that initial interactions between aggregates of derivative 3 and gold ions resulted in gold induced emission enhancement. However, during the sensing event the gold ions were reduced to gold NPs and the aggregates of derivative 3 were oxidized species of derivative 4 (vide infra) and the energy transfer between the gold NPs and aggregates of oxidized polymeric species 4 led to complete quenching of the emission intensity.38-40 The cyclic voltammogram of derivative 3 in H2O :CH3CN (1 : 9) (15 μL THF to dissolve) showed a reduction potential at and −0.37eV. In the presence of 60 equiv. of Au 3+ ions to derivative 3, when the reduction potential (−0.37 eV) was applied, a new band was observed corresponding to the LSPR band of Au NPs at 570 nm (30 min) (Figure S11, Supporting Information). These studies suggest the reduction of Au3+ ions to Au NPs in the presence of aggregates of derivative 3. The interactions between gold NPs and oxidized species of derivative 4 were also supported by the binding energy (BE) of the XPS spectrum. The weak S2p signal at 162 eV corresponding to sulphur was observed. The signal corresponding to Au 4f7/2 was shifted to 87.4 eV (approx. +3eV) compared to that of bare Au NPs which again suggest the interaction between gold NPs and polymeric species.41,42 Additional peak was observed at 283.16 eV corresponding to C1s of organic residue (Figure S12, Supporting Information). 7 ACS Paragon Plus Environment


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For the characterization of nanomaterials, the H2O/THF solution of derivative 3 and Au3+ ions was allowed to evaporate. The precipitates so obtained were washed thoroughly with organic solvents such as THF and chloroform. Afterwards, the precipitates and the residue obtained after evaporating the organic solvents were analyzed, separately. In the powder X-ray diffraction (XRD) studies the diffraction peaks were observed

at 38.2, 44.4, 64.6, and 77.5 (2θ )

corresponding to Au NPs43,44 (Figure S13a, Supporting Information). The selected area electron diffraction (SAED) pattern showed (111), (200), (220), (311) and (422) planes corresponding to Au NPs (Figure S13b, Supporting Information). The 1H NMR studies of the organic residue showed the broadening of all peaks (Figure S14, Supporting Information). After that derivative 3 and Au3+ ions were allowed to react under lab conditions. When the reaction (TLC) was accomplished, we isolated the product. The ESI-MS mass spectrum of the purified sample supported the formation of dimeric oxidized species of derivative 3 (Figure S15, Supporting Information). The wide angle XRD analysis of the oxidized species 3 showed the q values of 1.9 nm-1 corresponding to d spacing of 3.3 nm and a shoulder peak at 2.36 nm-1 which suggested the formation of supramolecular polymeric framework of thiophene appended PBI derivative 4 (Figure S16, Supporting Information). Further, the broad peak at 2θ = 25˚ is observed which corresponds to polymeric thiophene backbone which confirms our assumption regarding the polymerization of derivative 3 through thiophene ring (Figure S17, Supporting Information).45 We also carried out 1H NMR spectroscopic studies of derivative 3 in DMSO/ H2O mixture (8:2). After the addition gold ions the whole spectra get broadened which is attributed the formation of supramolecular polymer 4 (Figure S19, Supporting Information). In the presence of Au3+ ions (60 equiv), the transmission electron microscope (TEM) images of derivative 3 showed the transformation of spherical aggregates of derivative 3 to the sheet like structure. Over the surface 8 ACS Paragon Plus Environment

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of the polymeric sheet deposition of small spherical AuNPs (2-10 nm) was observed (Figure S20, Supporting Information). The HR-TEM image showed the d-spacing of 0.23 nm corresponding to the (111) plane of Au NPs (Figure S20, Supporting Information). All the above studies confirm our assumption that gold ions interacted with the supramolecular aggregates of derivative 3 and got reduced. Simultaneously, the aggregates themselves were oxidized to form polymeric species 4 and aggregates of oxidized species act as stabilizers for the AuNPs to generate supramolecular polymer 4: Au NPs (Figure S21, Supporting Information). The UV-vis. spectrum of polymeric species 4 in H2O/THF (4:6, v/v) exhibited absorption band at 496 nm and a small hump at 762 nm. (Figure S22, Supporting Information). In the emission studies, polymeric species in H2O/THF (4:6, v/v) showed the emission band at 536 nm (Figure S23 B). On addition of gold NPs to this solution, the emission intensity was fully quenched which may be attributed to the energy transfer between polymeric species 4 and Au NPs. Thus, the photophysical behaviour of isolated derivative 4 in H2O/THF (6:4, v/v) solvent mixture in the presence of Au NPs is similar to that observed in case of in situ generated supramolecular polymer 4 and Au NPs (vide supra). The possibility of energy transfer between oxidized species and Au NPs prompted us to evaluate the efficiency of in situ generated catalytic system in Heck coupling reaction under visible conditions. The activity of the photocatalyst was examined in the Heck reaction between iodobenzene and 4-vinylpyridine in the presence of potassium carbonate under aerial conditions in DMSO as solvent (Scheme 5). The reaction mixture was taken in the round bottomed flask which was dipped in water bath to prevent the photo-heating effect and a tungsten filament bulb (100W) was used as the irradiation source. After the completion of the reaction (1h, TLC) and desired product was obtained in 91% yield (see table 1, entry 1).We also examined the catalytic efficiency of the model reaction using solvent mixture such as DMSO, 9 ACS Paragon Plus Environment


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DMSO/ H2O (1:1) and H2O as the reaction media. All the reactions went smoothly and no significant effect on the yield of the final product was observed on changing the solvent system (see table 1, entries 1, 2 & 3). Keeping in mind the benign nature of H2O, we chose water as the solvent system for carrying out the further reaction. The same reaction when carried out under dark conditions yielded the desired product in trace amount which clearly emphasizes that reaction is light driven (table 1, entry 4). We also investigated the efficiency of catalytic system in absence and in the presence of higher amount of base. Interestingly, in the presence of higher amount (2 equiv) of K2CO3, the yield of the reaction was not affected (table 1, entry 5), however, without K2CO3, the transformation was not observed (table 1, entry 6) which suggests that basic medium is a perquisite for all. Further without catalyst the reaction was unable to proceed (table 1, entry 7). We performed several experiments to determine the role of organic component of the system, we performed several experiments. We carried out the reaction in the presence of polymeric species 4/ derivative 3 in the absence of Au NPs, both the reactions didn‘t proceed (table 1, entries 8 & 9). Then we prepared bare Au NPs by the method reported in literature.46 We carried out the model reaction in the presence of bare Au NPs in the model reaction. The reaction was accomplished in 6h in 48% yield (table 1 entry 10). The yield remain unchanged after the addition of aggregates of derivative 3 to the same reaction mixture (table 1 entry 11) while upon the addition of oxidized species, the desired product was obtained in 69% yield (table 1 entry 12). We also utilize the efficiency of hybrid nanomaterial Au@Fe3O4 encapsulated by hetero-oligophenylene assembly as the catalytic system in model reaction. The reaction took 5 h for the completion and target compound was obtained in 68 % yield (table1, entry13). Further emphasize the role of polythiophene species as the stabilizers for Au NPs, we also synthesized the derivative 7 (Scheme S2, Supporting Information) whose structure was confirmed by NMR 10 ACS Paragon Plus Environment

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Table 1: Heck coupling between various aryl halides and triflate with 4-vinylpyridine under photocatalytic conditions catalysed by supramolecular polymer 5: Au NPs.

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spectroscopic studies (Figure S33 in the Supporting Information). The UV-vis. absorption studies, powder X-ray analysis and TEM of derivative 7 in the presence of Au3+ ions showed the formation of Au NPs. (Figure S23 & 24, Supporting Information). We utilized the as prepared Au NPs for carrying out the model reaction under optimized photocatalytic environment, and the targeted compound was attained in 48 % yield (see table 1, entry 14). All the above results highlight the role of polythiophene species 4 in increasing the efficiency of catalytic system in Heck coupling reaction. With the optimized reaction conditions, we checked the scope of the reaction by employing various substituted aryl halides. All the reactions went smoothly by varying the substituents from electron donating to electron withdrawing (see table S2, entries 1-4, Supporting Information). After that we checked the effect of leaving group by using the phenyl triflate as one of the substrate. We carried out the reaction between phenyl triflate (prepared by the reported method) with 4-vinylpyridine under optimized photocatalytic conditions. The reaction was completed in 50 minutes to yield the desired product 10a in 90% yield (see table S2, entry 5, Supporting Information). Next, we explored the catalytic efficiency of the generated photocatalyst by involving the variety of aryl halides such as iodides, bromides and chlorides in reaction as one of the substrate. We carried out the Heck coupling of arylbromides such as bromobenzene, 4-bromoveratrole and 3,5. dimethylbrormobenzene with 4-vinyl pyridine. All the reactions were complete in 2h to furnish the desired compounds in excellent yields (see table S2, entries 6-8, Supporting Information). We also checked the efficiency of catalytic system by using aryl chlorides as one of the substrate. Aryl chlorides are known for their low reactivity in Heck coupling reaction and usually the reaction conditions require longer time to complete the reaction.47-49 We checked the 12 ACS Paragon Plus Environment

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efficiency of the supramolecular ensemble 4: Au NPs in reactions involving substituted aryl chlorides such as chlorobenzene and p-chloroaniline with 4-vinylpyridine (table S2 entries 9-11). All the reactions were complete in 6h and furnished the target compound in moderate yields. The reaction between 1-chloro-4-nitrobenzene and 4-vinylpyridine was completed in 10h and desired product was obtained in 57% yield. On the basis of these results, we believe that polymeric species serve as stabilizers for the in situ generated Au NPs and bring the reactant molecules closer to the catalytic sites. In the next part, we utilize the aliphatic as one of the substrate with various aryl halides. We carried out the reaction between methylacrylate with aryl halides such as iodobenzene, piodoanisole and 1-chloro-4-iodobenzene under optimized photocatalytic conditions. All the reaction went smoothly to attain the desired product in good to moderate yields (Table S3, entries 1-3, Supporting Information). We evaluated the efficiency of the photocatalytic system in the reaction between iodobenzene and vinylpyridine using various amounts of catalytic system (Table S4, Supporting Information ). When the amount of catalyst was 10000 ppm, the targeted product was attained in 89% yield (Table S4, entry 1) in 1 h and without catalyst the reaction didn‘t proceed. When the lower amount of catalyst was used i.e.1 ppm, the reaction was accomplished in 10h to furnish the desired product in 72% yield (Table S4, entry 8). Such an extremely low quantity of photocatalytic system has never been successfully used for Heck coupling before the present study. The reusability of the supramolecular polymeric ensemble 4: Au NPs was examined by carrying out the model reaction under photocatalytic optimized conditions. The catalyst can be reused upto seven times (Figure S25, Supporting Information). After the seventh cycle the yield of target compound was 73% yield. The TEM image showed slight change in the morphology of 13 ACS Paragon Plus Environment


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the catalytic system after seven cycles (Figure S26, Supporting Information). we carried out kinetic studies of recyclability experiment using UV-vis. absorption studies. For this we carried out the reaction between iodobenzene and 4-vinylpyridine as model reaction and determine the catalytic activity of catalyst after each cycle .These studies clearly suggest that catalyst has been deactivated after seventh cycle which may be attributed to the leaching of the catalyst. The kinetic graph of recyclability has been provided in the supporting Information (Figure S27 in the supporting information). The ICP analysis of the residue left after the seventh cycle showed the leaching of 0.133 ppm of the gold into the solution (Figure S28, Supporting Information). We also checked the reusability of oxidized species of derivative 7 stabilized Au NPs. Interestingly, Au NPs stabilized assemblies of derivative 7 exhibited almost no reusability. The TEM image of the catalytic sample after first cycle showed the aggregation of Au NPs (Figure S30, Supporting Information). These studies highlighted the role of oxidized polymeric species as stabilizing agents for in situ generated Au NPs. For the clearer perception of the mechanism of the reaction, we performed model reaction upon the addition of electron trapping agent (TEMPO). A significant inhibition of the catalytic system was observed which indicates that reaction is light driven. From the above experiments, we propose that under the photocatalytic conditions energetic electrons are transferred to the leaving group from the gold NPs to facilitate the cleavage of C-I bonds. This step is followed by fast insertion of alkenes to the above generated complex. Finally, β-hydrogen elimination resulted in the formation of product.13a A schematic representation of the mechanism of the photocatalytic Heck reaction is shown in scheme S3, Supporting Information. Having done all this, we examined the practical applicability of supramolecular polymer 4: Au NPs in Heck coupling reaction between hexaphenylbenzene (HPB) derivative 12 and 414 ACS Paragon Plus Environment

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vinylpyridine. Due to insolubility of the HPB derivative in aqueous media, the reaction was carried out in MeCN under optimized photoatalytic conditions. The desired product was obtained in 65 % yield (Scheme S4, Supporting Information). Next, we examined the efficiency of the supramolecular polymer 4: Au NPs in multifold heck coupling reactions. We carried out the reaction between cyclopentadienone derivative 14 and vinyl pyridine under photocatalytic conditions. The desired product 15 was obtained in 58% yield in 12h (Scheme S5, Supporting Information). Then, we chose 1,3,5-tribromobenzene (16) as one of the substrates and the desired product 17 was obtained in 62% yield in 12 h (Scheme S6, supporting Information). Thus, the as prepared catalytic system could be utilized for carrying out two/three fold Heck coupling reaction in a variety of substrates. In the next step, we planned to examine the catalytic efficiency of supramolecular polymer 5: Au NPs as supported catalytic system. In this approach, we prepared the portable ―dip catalytic strip‖ by dipping the filter paper in the concentrated solution (10 µM) of supramolecular polymer 5: Au NPs. Afterwards the filter paper was dried in an oven. This process was repeated several times. The loading of catalyst over filter paper is clearly visible to naked eye (Figure 30a & 30b). The SEM images of uncoated filter paper and coated filter paper clearly showed the deposition of catalytic system on it (Figure 30c & 30d). Afterwards, we checked the catalytic activity of this portable strip in Heck coupling reaction under visible conditions. The final product was attained in 87% yield after the completion of the (80 min). We also carried out the reaction by using this portable catalyst under dark conditions. Reaction didn‘t proceed at all. This shows the necessity of visible light for carrying out such reaction. The catalyst coated filter paper was recycled and dried after the completion of the reaction and can be reused upto eight times (Figure S31, Supporting Information). After the 8th cycle the catalytic activity was reduced and 40 % yield was obatined. 15 ACS Paragon Plus Environment


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We also examined the efficiency of dip catalytic strip in multifold heck coupling reaction between 1,3,5-tribromobenzene derivative 16 and vinyl pyridine, yielded final product in good yield (54%) after 5h. In conclusion, we designed and synthesised thiophene appended PBI derivative 3 which under undergoes oxidative polymerization in the presence of gold ions to generate supramolecular polymeric ensemble 4 and showed promising photocatalytic activity in Heck and multifold Heck coupling reactions with broad scope. The usefulness of this system is demonstrated by its high efficiency, wide scope and greener reaction conditions. Moreover, this catalytic system could be reused upto seven times and as prepared dip catalytic strip exihibited recyclability upto eight cycles. Furthermore, the utility of catalytic system as heterogeneous catalyst has been demonstrated by preparation of paper based recyclable ―dip catalytic strip‖ which exhibited high efficiency in Heck coupling reaction. EXPERIMENTAL SECTION Synthesis of photocatalyst: An aqueous solution of AuCl3 (10-1 M) was added into the solution of compound 3 [H2O/THF, 7/3; v/v]. This above solution mixture was allowed to stir at room temperature and the solution color changed from wine red to purple within 30 minutes and the formation of Au NPs took place (confirmed by recording UV-vis. absorption studies). Then 0.25 ml of this solution was utilized in the Heck and multifold Heck coupling reaction.

ASSOCIATED CONTENT Supporting Information. ―The contents of the SI section include 1H, 13C, ESI-MS and FT-IR spectrum of compounds 4, 5, 7, 10a-h, 13, 15 &17; UV-vis and fluorescence studies; SEM, 16 ACS Paragon Plus Environment

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TEM images; powder XRD, Raman analysis; DLS, XPS studies, and table of comparison of present manuscript with previous reports.‖

AUTHOR INFORMATION Corresponding Author * E-mail: [email protected] Notes Authors declare no competing financial interest. ACKNOWLEDGMENT V.B. is thankful to SERB, New Delhi (ref. no. EMR/2014/000149) for financial support. We are also thankful to UGC (New Delhi) for ‗‗University with Potential for Excellence‘‘ (UPE) project. M.K. is thankful to DST for the INSPIRE fellowship.

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(48) Yu, L.; Huang, Y.; Wei, Z.; Ding, Y.; Su, C.; Xu, Q. Heck Reactions Catalyzed by Ultrasmall and Uniform Pd Nanoparticles Supported on Polyaniline J. Org. Chem. 2015, 80, 8677−8683, DOI 10.1021/acs.joc.5b01358.

(49) Lin, Y.-C.; Hsueh, H.-H.; Kanne, S.; Chang, L.-K.; Liu, F.-C.; Lin, I. J. B. Efficient PEPPSI-Themed Palladium N-Heterocyclic Carbene Precatalysts for the Mizoroki-Heck Reaction. Organometallics 2013, 32, 3859−3869, DOI 10.1021/om4003297.



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Synopsis: Gold NPs based photocatalyst excellently replaced palladium based catalytic system and provide the greener, portable catalyst for Heck Coupling reactions.


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Graphics for manuscript

Perylene bisimide (PBI) derivative 4 having thiophene moieties at the bay positions has been designed and synthesized. Derivative 4 forms J-aggregates in aqueous media and these aggregates served as reactors for the generation of Au NPs and themselves underwent oxidative polymerization through thiophene moieties to generate polymeric species 5. As prepared polymeric species 5 and gold NPs generated supramolecular ensemble 5: Au NPs which served as promising photocatalytic system for Heck and multifold Heck coupling reaction. Moreover, the work being presented in this manuscript demonstrates the deposition of supramolecular ensemble 5: Au NPs on paper strips for preparation of “dip catalytic strip” as an efficient, economic, efficient, green, portable and recyclable catalytic system. The efficiency of this catalytic system is evident from its broad scope, benign reaction conditions, multifold Heck coupling, seven times reusability (in solution form) and eight times reusability (“dip catalytic strip”).

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Gold nanoparticles immobilized polymeric PBI derivative: Productive

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