molecular recognition of carboxylic acids and … recognition of carboxylic acids and carboxylates:...

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Molecular Recognition of Carboxylic Acids and Carboxylates: A Review

Mahasish Shome, Nakul Mishra*

Department of Chemistry, School of Chemistry, University of California, Davis, USA.

Received 30th October 2015; Revised 12th November 2015; Accepted 26th November 2015

ABSTRACTThis review focuses on molecular recognition of carboxylic acids and carboxylates. Carboxylic acids (or carboxylates) are the common functional group in synthetic organic chemistry and biological chemistry and have attracted scientists to develop different approaches for their recognition. The binding of carboxylic acids by the designed receptors is of colossal attention to invent many biological events in the field of molecular recognition research. Synthetic receptors of appropriate shape and size can bind to the guest easily while others not having high binding affinity are often added with spacers to make it compatible with the guest. Multiple hydrogen bonds and π-stacking surfaces contribute to high binding constant between the host and the guest.

Key words: Host-guest chemistry, Carboxylic acid, Synthetic receptors.

1. INTRODUCTIONCreation of new molecules with exotic architecture and useful functions is an area that will continue to stimulate the imagination of chemists. The molecular recognition chemistry has focused on non-covalent binding and has succeeded in mimicking various phenomena in nature. Among the biomolecules, peptides, constituted from the versatility to generate diverse (polar, hydrophobic, acidic, basic, neutral, nucleophilic, and electrophilic) environments, are particularly amenable to design and provide unlimited scope to craft new molecules with unusual properties [1]. The advance of synthetic receptors for a chosen substrate (host-guest chemistry) is a well-established area of research, and selective receptors have now been described for a whole range of substrates, from simple metal cations to polyfunctional molecules such as peptides, proteins, nucleic acids, and carbohydrates [2-7]. Recent progresses in chemistry have provided us the ability to design unnatural molecules, to predict their properties, etc. Numerous efforts have been devoted to the development of biotic as well as abiotic receptors for dicarboxylic acids and its derivatives. Organic carboxylic acids and its derivatives take part in an essential role in a wide range of chemical and biological processes. Carboxylic acids and carboxylates ion are particularly common functional groups in natural and biological systems. It was inspired for developing of a number of different approaches for their recognition. This has been especially true during the last 30 years, and there have been a number of reviews describing the chemistry of

recognition and related to host-guest chemistry. The purpose of this review is to summarize the different approaches that have been taken to carboxylic acid and carboxylate recognition reviewing the literature up to level best.

2. IMPORTANCE OF CARBOXYLIC ACID RECOGNITIONRecognition of carboxylic acids through design and synthesis of artificial receptors is an important aspect in molecular recognition research. Dicarboxylic acids and carboxylates are biologically relevant 1, 2 species, and consequently there is a continuous interest in the design and synthesis of receptor molecules, which show selective binding of dicarboxylic acid [8]. Binding is an essential factor for the existence and reactivity of a compound. Carboxylic acid moiety is in attendance in various biologically active molecules in nature as well as it essences in numerous metabolic processes. Drugs such as antibiotics (e.g., penicillin, ciprofloxacin, etc.), analgesics, anti-inflammatory, and the other bioactive molecules such as bilirubin, bile acids, folic acid, ascorbic acid (Vitamin C), and biotin (Vitamin H), all are having carboxylic acid moiety as the main functionality. Carboxylic acid used as di- and tricarboxylate in carboxypeptidase enzyme is also of interest. This is an essential component of numerous metabolic processes including the citric acid and glyoxylate cycles and involved in the generation of high-energy phosphate bonds [9]. That’s for carboxylic acid receives a position in chemistry-biology, and the

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*Corresponding Author: E-mail: [email protected]

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recognition of carboxylic acids is an important aspect in the area of molecular recognition, accordingly.

3. STEREOELECTRONIC FEATURE AND SELF-ASSOCIATION BEHAVIOR OF CARBOXYLIC ACID GROUPThe conformational features of the carboxyl group, ester, and amides were discussed first by Leiserowitz and Schmidt [10]. The geometry and the conformations of the carboxyl group have been solved from their crystal structures. Gandour [11] pointed the stereo-electronic features of carboxyl oxygen with the O-H group, which preferred either in a syn-planar or anti-planar conformation in the crystalline phase (Figure 1).

Monocarboxylic acids are generally present as dimeric or highly associated forms. If the molecule is small, it may interlink by single O-H…O bonds to form a chain motif in which the hydrogen bonds are almost linear, and the O-H proton donor lies in the plane of the carboxylic system [12]. Infrared spectrum revealed that gaseous monomeric formic acid exists in the syn-planar structure, which is more stable by 2.0 Kcal mol−1. Although, microwave studies have reported that the difference was at least 4.0 Kcal mol−1. The anti-planar form arises when the O-H bond participated in an intramolecular O-H…O bond, particularly in 1, 2-disubstituted dicarboxylic acids (3) [13].

Some discrepancies have been found in a rare case of o-methoxybenzoic acids, where the acid is not interlinked rather than it forms an intramolecular O-H…O (OMe) hydrogen bond via an anti-planar conformer as shown in compound (4) (Figure 2).

An example of syn-planar conformer was found by Jonsson in acetic acid crystal [14]. Acetic acid yields the cyclic co-planar dimer so that a methyl C-H bond is directed to be involved forming a C-O…H contact of 1.697 and 1.699 Å.

4. MONOCARBOXYLIC ACID RECOGNITIONCarboxylic acids are popular substrates in supramolecular chemistry which bind to other chemical compounds through hydrogen bonding, electrostatic interactions, and donor-acceptor interactions [15]. Geib et al. and later many scientists used 2-aminopyridine as hydrogen bonding motif with a suitable spacer for carboxylic acid binding [16]. Etter has pointed out that the strongest hydrogen bond acceptor will bind to the strongest donor [17]. Thus, the carboxylic acid and aminopyrimidine groups would be expected to form hydrogen bond to each other rather than form symmetrical dimers. In the formation of hydrogen bonded infinite ribbons in 1:1 molecular complex of 2-aminopyrimidine and succinic acid, Etter and Adsmond first demonstrated the promise of

the 2-aminopyrimidine group as a –COOH binding site [18].

Goswami et al. have demonstrated the carboxylic acid recognition within the semi-rigid and somewhat flexible isophthaloyl spacer having pyridine amide and an additional aliphatic or aromatic amide moiety to give rise to tighter binding to a monocarboxylic group compared to simple pyridine-2-amide binding to the monocarboxylic group. They used this spacer for monocarboxylic acid receptors having an aliphatic amide linking to form an extra hydrogen bond with CO2H group (three point hydrogen bonds), and thus it binds stronger to CO2H compared to two-point hydrogen bond with simple pyridine-2-amide (Figure 3) [19].

In a similar way, various groups are involved in molecular recognition research and devised an array of synthetic receptors for monocarboxylic acids and its

Figure 1: Conformational structures of the carboxyl group.

Figure 2: Intramolecular and intermolecular hydrogen bonds formation in carboxylic acid leading to syn- and anti-conformers.

Figure 3: Isophthaloyl spacer gives rise to tighter binding to monocarboxylic group.

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derivatives also. Crego et al. synthesized the receptors for monocarboxylic acids and amino acids, based on three points hydrogen bonding setting to the binding pocket of the receptors (Figure 4) [20].

Moore et al. have synthesized the receptors containing five and six membered bowl shaped lactam ring for carboxylic acid. The receptor had a tricyclic structure with a bowl shape and a carboxamide moiety at the end of a flexible arm. Upon performing 1H nuclear magnetic resonance (NMR), for the determination of association constant of the receptor and benzoic acid, it was found to be 80 M−1 in good agreement with a two binding points process [21]. Wu et al. have designed fluororeceptors based on thiourea and amide groups for the recognition of dicarboxylates. Receptors had a better adipate anion selectivity compared to other dicarboxylates. In addition of the guest solution fluorescence intensity was gradually quenched at 393 nm for the case of receptor having naphthalene moiety. However, the fluorescence intensity was enhanced when the receptor contained electron withdrawing group like p-nitrophenyl group (Figure 5) [22].

Cuevas et al. have designed two flexible receptors for carboxylic acids, based on 1-amino-3-fluoro-2-alcohol functional arrays and built on aminomethyl pyridine platforms. The C2-symmetric one (from 2,6-bis(aminomethyl)pyridine) has been shown to be an efficient cross-sectional area due to its ability to form geometrically different diastereomeric complexes enabling the discrimination between the enantiomers of a series of carboxylic acid in the 1H NMR spectra [23].

Vicent et al. made the design of synthetic cavities with binding groups in complementary positions to the hydrogen bonding sites on peptides. The receptors were reported in Figure 6 for acylamino acid (L-proline) and show a systematic increase in binding affinity from 410 M−1 to 2600 M−1 as the number of hydrogen bonding points increased [24,25].

Based on the incorporation of the several hydrogen bonding points, Raposo et al. designed and synthesized xanthone based chromenone for the monocarboxylic acids and amino acid (benzoylamino acid) recognition. It bears the required alignment and binding groups to associate with carboxylic acids based on three points hydrogen bonding in the binding pocket (compared with Goswami’s receptors). Additional stabilization may be accomplished with a charge transfer interaction between an electron-rich aromatic ring in the host and an electron deficient moiety in the amino acid derivative [Figure 7] [26].

However, it was found that simple charge stabilization was not sufficient for strong binding of arginine and

Figure 4: Receptors based on three point hydrogen bonding.

Figure 5: Lactam-based receptors for carboxylic acid.

Figure 6: Binding affinity increases on increasing hydrogen bonding points.

Figure 7: Xanthone-based chromenone for recognition of carboxylic acid and benzoylamino acid.

lysine side chains. High pre-organization of hydrogen bonding sites on a receptor and size complementarity between a receptor’s cavity and a guest made a great contribution to the stabilization of a complex. Simple modifications of these receptors, such as introducing groups for attachment to other host molecules, should produce useful building blocks for construction of receptors capable of recognizing particular peptides and proteins [27].

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5. DICARBOXYLIC ACID RECOGNITIONLike monocarboxylic acids, di- and tri-carboxylic acids are also biologically important, and their recognition is also a contemporary interest in the supramolecular community. In this aspect, different synthetic receptors of different topologies are notable in the literature. Garcia-Tellado et al. used 2-aminopyridine moiety as hydrogen bonding motif for the recognition of carboxylic acids which was related to the case of their selective binding by synthetic receptors. The receptors, where 2-aminopyridine derivatives were linked to an isophthalic acid spacer with wide range applications have been reported to bind barbiturates, mono and dicarboxylic acids (Figure 8) [28,29].

The macrocyclic sensor (20) shows a greater quenching response for diethylmalonic acid (Ka ~ 104 M−1) than the open form with size selective glutaric acid (Ka ~ 103 M−1). Design of synthetic receptors for neutral molecule is based on the interactions, e.g., hydrophobic, hydrogen bonding and π-stacking with the complementarity between the host and the guest [30,31]. Furthermore, as Shorthill et al. have shown, the fluorescence properties can allow the sensitive detection of complexes formed between guest molecules and such naphthalene ring based receptors [32].

At the same time, Garcia-Tellado et al. reported that if the length of the spacer and that of the guest carboxylic acids is quite fit, a tight 1:1 complex will be formed (22,23) [33], but when the carboxylic acid was longer than the receptor cavity size, an alternative mode of binding was observed in the form of infinite ribbons. In this regards, a variety of aromatic spacers ranging from simple phenyl to more complex, naphthyl, biphenyl, and terphenyl units have been used to create cavities of different sizes for accommodating dicarboxylic acids of different lengths. The study with straight chain diacids containing four, eight, and twelve carbon spacers was reported [34] within a variety of aromatic spacers to generate cavities of different sizes for the recognition of dicarboxylic acids of varied lengths (Figure 9) (24).

The dynamic supramolecular structures were also observed by increasing the chain of the dicarboxylic acid beyond the optimum. By increasing the length of dicarboxylic acid, the formation of ribbon or helical supramolecular structure was also obtained. The stability of supramolecular structure can be enhanced by an entropic effect if additional binding sites are present in the host molecule. Karle et al. synthesized adamantyl spacer-linked several bis-pyridine amide receptors, in which it was nicely applied for complexation with different dicarboxylic acids [35]. All bis-amides having the two-amide groups separated by a rigid linker are good candidates for forming linear aggregates of tapes and zigzag ribbons (Figure 10).

Figure 8: (18), (19) 2-Aminopyridine-based receptor for dicarboxylic acid recognition, (20), (21) 2-Aminopyridine moiety as hydrogen bonding motif for the recognition of dicarboxylic acids.

Figure 9: Binding of carboxylic acids with receptors having varied aromatic spacers.

Figure 10: Ribbon or helical supramolecular structure obtained increasing the length of the dicarboxylic acid chain.

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Goswami et al. engaged to elaborate the different hydrogen bonding patterns with synthetic receptors and dicarboxylic acids in phase directing system. An interesting hydrogen bonding pattern with genuine supramolecular arrangement of a ditopic receptor with dicarboxylic acids was reported with some abnormal behavior of flexible receptor as well as 1,4-phenylenedicarboxylic acid in solid state. The pyridine amide moieties were pointed toward the center of all the receptors, but the reverse attempts are taken in the cases to construct the receptor outside the center and linked through a flexible aliphatic spacer. Single crystal X-ray analysis of the complex shows the binding of pyridine amide groups of receptor are in syn-mode, and it has forced to bind carboxylic acids also in the syn-fashion. So, the beauty of the receptor is that the aliphatic spacer behaves such as a rigid aromatic receptor and binds dicarboxylic acid containing phenylene group creating a stair-like supramolecular network (Figure 11) [36].

Hydrogen bonds and other weak interactions force complexation in energetically favorable syn-form of 1,4-phenelynediacetic acid to bind in a polymeric fashion. In a different case, simple lower energetic anti-anti polymeric complex has been exclusively found. The other case with the ditopic receptor having no spacer has been employed for the recognition and which formed an exclusively anti-anti polymeric complex (Figure 12) [37].

It is noteworthy to compare the binding ability of hindered 2-pyridyl-pivaloylamide moiety and

2-pyridyl-acetamide as the bulky pivaloyl group is the main countable factor. It was reported an anti-anti polymeric hydrogen bonded complex of a ditopic bipyridyldipivaloylamide receptor with 1,4-phenylenediacetic acid and adipic acid as the guest substrate. The X-ray analysis has produced a nice stair-like anti-anti wave like in the network of polymeric complex.

A confliction has been found in recognition of a dicarboxylic acid in solution as well as in the solid phase by the pyridyl urea based pseudoditopic receptor has been studied. Intramolecular hydrogen bonding inhibits both the pyridine ring nitrogen’s from forming hydrogen bonds with the carboxyl group and force the receptor to behave in a monotopic manner, using the syn-urea amide moiety to bind carboxyl group of a dicarboxylic acid to form a 2:1 complex compare to monocarboxylic acid (Figure 13) [38].

A redox-active residue with about 3.2 Å inter-ring distance and having a catalytically active group make ferrocene as a useful spacer in the production of different receptors for dicarboxylic acid recognition (31). Medina et al. have stressed the importance of this correct functional group orientation and in achieving complexation of some synthetic receptors with the dicarboxylic acids [39]. Extending this work, Moriuchi et al. have reported the ferrocene receptor bearing the podand dipeptide chains (-L-Ala-L-Pro-NHPyMe), which was found to provide a chirality-based binding site regulated through two intramolecular interchain hydrogen bonds between CO (Ala) and NH (another Ala) of each podand dipeptide chain. The size selective and chiral recognition of dicarboxylic acids was achieved by multipoint hydrogen bonds at the binding site [40]. Unlike the interesting Kemp acid, several sites on ferrocene can be readily functionalized. When this feature is added to the possibility of altering binding behavior using redox chemistry, it is seen that the present systems hold considerable promise as a family of molecular receptors having variable properties (Figure 14) (32).

Recognition of hydroxy dicarboxylic acids such as tartaric acid, insoluble in chloroform was also achieved (Figure 15) [41]. Although 1H NMR signals

Figure 11: Stair-like receptors linked through aliphatic spacer.

Figure 12: Stair-like anti-anti polymeric complex formed by 1,4-phenelynediacetic acid and adipic acid.

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of the guest significantly broaden in the presence of the host at room temperature, the signals remarkably sharpen at low temperature and each free and bound guest gives clearly separated signals at −40°C. The resonance of the guest molecule show significant up-field shift and lose the C2-axis of symmetry character upon complexation (Figure 15) [42].

Changing spacers, Ray et al. have succeeded in the synthesis of an artificial receptor based on pivotal ether or thioether linkage, hinged with two symmetrical arms of p-substituted phenyl with thiophene moiety as core structure. By fine tuning these molecules with amide functionalities, they demonstrated that these synthetic receptors can form strong complexes with appropriate dicarboxylic acids [43]. Similar to the shape of Ray’s receptor, Ghosh and Masanta designed and synthesized triphenylamine-based chemosensors, for the selective recognition of dicarboxylic acids. After examining the binding constant of chemosensors and carboxylic acids using 1H NMR, it was found to have selective recognition for glutaric and adipic acids (Figure 16) [44].

One of the recent approaches for the design of fluorescent signaling systems is to exploit photoinduced electron transfer (PET) in fluorophore-spacer receptor systems where the PET process is suppressed or enhanced by the introduction of a substrate into the receptor, exhibiting a fluorescent signal. The adenine-based fluorescent receptor was designed and synthesized for the selective recognition of dicarboxylic acids in CH3CN. The recognition takes

place through the Hoogsteen binding site of adenine with concomitant PET quenching of the anthracene moiety (Figure 17) [45].

Triphenylamine and anthracene-based chemosensors have been studied for selective recognition of dicarboxylic acids, keto, and hydroxyl monocarboxylic acid by Ghosh and Masanta [46]. Carboxylic acid binding takes place through charge neutral pyridyl amide receptor sites with simultaneous quenching of fluorescence of the triphenylamine moiety (Figure 18).

Ghosh and Adhikari also modified some novel quinoline-based receptor that shows monomer emission quenching followed by intramolecular excimer emission upon hydrogen bond complexed tartaric acid (Ka ~ 105 M−1) over rac-malic acid and succinic acid [47]. Adequately, it has been described a simple sensor bearing a hydroxyl group, which shows significant α-keto acid binding ability (Ka ~ 102 M−1) with pyruvic acid [48].

6. TRICARBOXYLIC ACID RECOGNITIONFor the detection of citric acid in less polar solvents, a quinoline-based tripodal fluororeceptor has been designed and synthesized by Ghosh and Adhikari receptor 36 shows monomer emission quenching followed by excimer emission upon hydrogen

Figure 13: Complexation in carboxylic acid moiety (29), actual complexation as revealed by single crystal X-ray structure (30).

Figure 14: Ferrocene-receptor for selective recognition of dicarboxylic acid.

Figure 15: Receptors of hydroxy dicarboxylic acids.

Figure 16: Synthetic receptor based on pivotal ether or thioether linkage (X=O/S).

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bond-mediated complexation of citric acid. In comparison, receptor 37, in the presence of citric acid, gives rise to a decrease in the monomer emission of the naphthyl moiety without showing any peak for the excimer. Receptor 36 was found to bind citric acid more strongly than receptor 37 in CHCl3 (Figure 19) [49].

7. CARBOXYLATESCamiolo et al. have used 2,5-diamidopyrrole containing “cleft-mode” anion receptor, which was able to form three hydrogen bonds to a benzoate anion in acetonitrile-d3 and forms a three point hydrogen bonding motif in solid state. The receptor was selective for benzoate over other putative anionic guests with association constant 2500 M−1 [50]. On the other hand, Kondo et al. have demonstrated a simple disulfonamide bearing hydroxyl group, which shows remarkable monocarboxylate anion-binding ability in acetonitrile-d3 at 298 K [51]. The hydroxyl groups of the receptor act as hydrogen bond donors in anion recognition even in such a polar solvent (Figure 20).

A flexible receptor containing thiourea and amide moiety was synthesized for aliphatic dicarboxylate anion. The fluorescent PET chemosensors possessing

two binding sides were designed by Gunnlaugsson et al. for the recognition of anions such as dicarboxylates and pyrophosphate; the anion recognition in dimethyl sulfoxide (DMSO) took place through two charge neutral thiourea receptor sites with concomitant PET quenching of the anthracene moiety (Figure 21) [52].

Liu et al. have found that the receptor has an ability to show distinct color change from light yellow to orange-red upon the addition of adipate ion in DMSO.The same type of work with calix[4]arene receptors for dicarboxylate anion show the chain length selectivity for the recognition of carboxylate anion [53].

Ranganathan has found that pyridine-bridged cystinophanes act as excellent hosts for 1, ω-alkane dicarboxylates. Cystine-based 26-membered hybrid cyclopeptides containing two cyclic repeats of Pyr-Cyst (Pyr=2,6-pyridine dicarbonyl and Cyst=cyst-diOMe) units and were found to bind a number of 1, ω-alkane dicarboxylic acids [(CH2)n-(COOH)2, n=1-4] with maximum affinity (Kassoc=3.69 × 102 M−1) and selectivity for glutaric acid (n=3) tetrabutylammonium salt (Figure 22) [54].

Research in Goodman’s group found that a thiourea-functionalized terpyridine unit can be a well-ordered recognition site for dicarboxylate ions in the presence of ruthenium (ɪɪ). Strong binding to the self-assembled receptor was found and an association constant >104 were measured [55].

Figure 17: Adenine-based fluorescent receptor for dicarboxylic acids recognition.

Figure 18: Anthracene-based chemosensor for dicarboxylic acid recognition.

Figure 19: Quinoline-based receptor for recognition of tricarboxylic acid.

Figure 20: Three hydrogen bonds in benzoate complex in solid state (38), disulfonamide bearing hydroxyl group shows remarkable anion-binding ability in MeCN-D3 (39).

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8. ENANTIOSELECTIVE CARBOXYLIC ACID RECOGNITIONWith the development of the combinatorial chemistry technique, 1, 1’-binaphthyl unit has been synthesized and could provide both excellent chiral recognition capability and interesting fluorescence signals. A huge defy has been undertaken to analyze the chiral composition of these compounds because of the inherently slow separation techniques. With the use of a fluorescence microplate reader or a fluorescence imaging technique, hundreds of samples can be analyzed very quickly. It was identified that the macrocyclic compound (S)-40, with two 1,1’-binaphthyl and two 1,2-diphenylethylenediamine units was capable of enantioselective fluorescent recognition exhibiting emissions both from the monomer as well as an excimer. The enantioselective fluorescent response of (S)-40 in the presence of mandelic acid was high for the emission of the excimer, but much smaller for that of the monomer (Figure 23) [56-58].

Zheng and Zhang have represented that chiral calix[4]arenes were good enough to discriminate enantiomers of R-hydroxy carboxylic acids (Ka ~ 103 M−1) and display a highly selective recognition between enantiomers of carboxylic acids (Figure 24) [59].

9. CARBOXYLIC ACID AS A BINDING MOTIF FOR VARIOUS GUESTSGiven the importance on the hydrogen bonding feature of carboxylic acids, several types of receptors containing carboxylic acid moiety as binding site have been devised. Rebek et al. designed and incorporated carboxyl groups in a convergent molecular cleft using endo-receptor principle with kemp triacid where carboxylic acid groups act as hydrogen bonding sites for complexation with the guest molecule. The binding of diacids of appropriate size and shape restricted the rotation in the stabilized complex (Figure 25) [60,61].

U-shaped 2,7-di-tert-alkyl-9,9-dimethylxanthene-4,5-dicarboxylic acids for the construction of molecular hosts were also synthesized by the Rebek group. Condensation of two diacid units with spacers (e.g., hydroquinone, 4,4’-biphenol, and 2,6-diaminonaphthalene) gave large structures capable of assuming clefts such as shapes that complex sizable guests such as DABCO, quinine, quinidine, and quinoxaline-2,3-dione (Figure 26) [62].

Acidity and hydrogen bonding capacity are crucial factors in molecular recognition research. Chen and

Figure 21: Thiourea receptor for aliphatic dicarboxylate anion.

Figure 22: Cystinophanes as a host for dicarboxylate.

Figure 23: Chiral recognition of mandelic acid by a receptor having two 1,1’-binaphthyl and two 1,2-diphenylethylenediamine units.

Figure 24: Chiral recognition of carboxylic acids by calix[4]arene.

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Siegel successfully correlated space polar-π effects on the acidity of carboxylic acids groups [63]. Zimmerman and Weiming have achieved a receptor type, which provided fewer hydrogen bonding interactions, but contribute a single π-stacking surface. In this receptor (molecular tweezer), the binding site was created by the convergence of two aromatic surfaces and a carboxylic acid. These cleft-like receptors retained the exceptional complexation power of the naphthalenophanes, but can bind much larger guests such as the nucleotide base adenine. Hydrogen bonding and “π-sandwiching” to a single edge of adenine can result in exceptional binding affinity (Figure 27) [64].

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*Bibliographical Sketch

I completed my High school from Visakhapatnam, Andhra Pradesh, India. I qualified IIT-JEE and got admitted into IIT Dhanbad with a major in Chemistry. I was selected as a summer intern at Monash University, Australia. My work was published on Journal of American Chemical Society (doi: 10.1021/ic402672m). Then I joined University of California, Davis and performed the research in collaboration with my group member Nakul Mishra.

molecular recognition of carboxylic acids and … recognition of carboxylic acids and carboxylates:...

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