Guest-induced capsular assembly of calix[5]arenes

Garozzo, Domenico; Gattuso, Giuseppe; Kohnke, Franz H.; Malvagna, Paola; Notti, Anna; Occhipinti, Sergio; Pappalardo, Sebastiano; Parisi, Melchiorre F.; Pisagatti, Ilenia

doi:10.1016/s0040-4039(02)01847-6

Cited by 37 publications

(36 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The 1 H NMR spectra of the inclusion complexes of calix [5]arenes with alkylammonium guest ions normally show distinct signals for the free and complexed host and guest species in slow exchange on the 1 H NMR timescale. [13,14,18] Here, signals corresponding to the free host and guests could barely be seen in the spectra of equimolar host-guest mixtures of 1 with the longer alkyldiammonium (C 12 -C 16 ) dichloride salts, which suggests very high association constants (K a > 10 6 m À1 ) for the formation of the capsular (C-shaped) 1:1 host-guest complexes with C s symmetry. Similar results were observed using other solvent systems (including neat (CDCl 2 ) 2 , CDCl 3 , and CD 2 Cl 2 , or mixtures thereof with up to 50 % content of CD 3 OD), or on changing-in the case of C 12 -the nature of the counteranion (diacetate, dibromide, and dipicrate salts).…”

mentioning

confidence: 94%

“…[5c, 7] The molecular recognition of a,w-alkanediyldiammonium salts has been actively investigated with different classes of artificial homo(poly)topic receptors. Among these, cylindrical macrotricyclic hosts, [8] cucurbiturils, [9] crown ether [10] and glycoluril derivatives, [11] bimetallic porphyrin dimers, [12] as well as p-tert-butylcalix[5]arenes [13] have been employed. However, none of the receptors used so far has been equipped with complementary counterion-binding sites.…”

mentioning

confidence: 99%

“…ESI-MS exploits the remarkable tendency of the p-basic calix [5]arene cavity to include alkylammonium guests, thus providing ion labels for the detection of encapsulated complexes in the gas phase. [13,17,18] The affinity of 1 for a,w-alkanediyldiammonium dichloride salts was initially investigated by 1 H NMR titration experiments in (CDCl 2 ) 2 /CD 3 OD (2:1 V/V). Addition of the guest salt (up to 4 equivalents) to a solution of 1 (1.0 10 À3 m) caused the formation of very strong inclusion complexes, whose host-guest stoichiometries (1:1 and/or 2:1) and geometries depend on the length of the diammonium ion and the [host]/[guest] ratio (see Figure 1).…”

mentioning

confidence: 99%

See 2 more Smart Citations

A Calix[5]arene‐Based Heterotetratopic Host for Molecular Recognition of Long‐Chain, Ion‐Paired α,ω‐Alkanediyldiammonium Salts

et al. 2005

Self Cite

View full text Add to dashboard Cite

Ion-pair recognition, that is, the simultaneous complexation of cation and anion guest species by neutral hosts, is an emerging field of topical interest in supramolecular chemistry with great potential for biological, analytical, and environmental applications.[1] It is well known that the ion-binding process with neutral receptors is adversely affected by the ionpairing of guest salts, [2] so that it is common practice to make use of salts with weakly coordinating counterions, [3] which result in enhanced host-guest associations. On the other hand, the ion-pairing interference can be circumvented either by using an appropriate combination of anion and cation receptors (binary host strategy) [4] or by designing specific heteroditopic receptors that take advantage of favorably positioned binding sites as well as induce positive cooperative and allosteric effects.[5] So far a plethora of heteroditopic receptors have been developed for inorganic ion pairs, [6] but much less has been reported for organic salts. [5c, 7] The molecular recognition of a,w-alkanediyldiammonium salts has been actively investigated with different classes of artificial homo(poly)topic receptors. Among these, cylindrical macrotricyclic hosts, [8] cucurbiturils, [9] crown ether [10] and glycoluril derivatives, [11] bimetallic porphyrin dimers, [12] as well as p-tert-butylcalix[5]arenes [13] have been employed. However, none of the receptors used so far has been equipped with complementary counterion-binding sites.Following our specific interest in the development of neutral multisite receptors for biogenic (poly)ammonium salts, [14] we report herein the synthesis and unique molecular recognition abilities of the first heterotetratopic receptor, 1, which consists of two convergent, conformationally fixed, cone calix[5]arene units (cation-binding sites) that are covalently linked at their upper rims by means of a 1,4-bis(ureido)phenylene spacer (anion-binding sites). Host 1 readily forms overall charge-neutral, unimolecular capsules (ligand-separated ion-pair complexes) of nanoscale dimensions by tight encapsulation [15] of linear a,w-alkanediyldiammonium ions, which range from 1,12-dodecane-to 1,16-hexadecanediammonium, inside the inner space defined by the two converging calix [5]arene cavities by simultaneously binding each of the two counteranions to the peripheral ureido functions through hydrogen bonds.The target biscalixarene 1 was synthesized in six steps from the known 31-benzyloxy-p-tert-butylcalix[5]arene (2) [16] according to the sequence illustrated in Scheme 1. The exhaustive O-alkylation of 2 with 4-methylpent-1-yl tosylate and K 2 CO 3 in CH 3 CN at reflux produced pentaether 3 in 77 % yield which, upon Pd/C-catalyzed hydrogenolysis in EtOAc, gave monohydroxy intermediate 4 in 93 % yield. The Scheme 1. Synthesis of 1: a) TsO(CH 2 ) 3 CH(CH 3 ) 2 , K 2 CO 3 , CH 3 CN, reflux, 12 h, 77 %; b) H 2 , Pd/C, EtOAc, room temperature, 4 h, 93 %; c) 68 % HNO 3 /AcOH, CH 2 Cl 2 , 08C, 25 min, 77 %; d) TsO(CH 2 ) 3 CH-(CH 3 ) 2 , NaH, ...

show abstract

mentioning

confidence: 94%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

A Calix[5]arene‐Based Heterotetratopic Host for Molecular Recognition of Long‐Chain, Ion‐Paired α,ω‐Alkanediyldiammonium Salts

et al. 2005

Self Cite

View full text Add to dashboard Cite

show abstract

“…5 Thus, only a few examples of calix [6]arenes bearing ester 6 groups as well as crown ether 7 or aza-cryptand 8 units have been described. 9 With such receptors, the host-guest recognition may involve π-cationic, CH-π, π-π interactions and hydrogen-bonding. The use of electrostatic interactions for the binding of ammonium ions by calix [6]arene hosts was also reported.…”

Section: Introductionmentioning

confidence: 99%

Calix[6]arene Tris-carboxylic Acid Derivatives: X-ray and NMR Characterization of their Remarkable Host-guest Properties Toward Ammonium Ions

Gac

Giorgi²,

Jabin

2007

Supramolecular Chemistry

View full text Add to dashboard Cite

International audienceThe ability of calix[6]arene tris-carboxylic acid derivatives to include ammonium guests has been investigated both in solution and in the solid state. NMR studies and crystallographic data showed that the highly flexible calix[6]arene structures can be shaped in a well defined cone conformation thanks to the formation of an ion-paired cap between the carboxylate groups of the calixarene and their ammonium counter-ions. The resulting supramolecular edifices exhibit remarkable host-guest properties toward ammonium ions even in polar and protic solvents. The recognition process has been rationalized in the solid state by the combination of hydrogen bonding, electrostatic and CH-Π interactions, and a remarkable C3-complementarity between the well-organized binding carboxylates of the host and the ammonium guest. Very interestingly, the endo-cavity complexation of large polycyclic ammonium ions as well as bioactive ammonium ions has been clearly demonstrated through NMR spectroscopy. Finally, the tuning of the nature of the ammonium ions involved in the supramolecular cap led to highly responsive molecular receptors

show abstract

“…The conformational characteristics and complexation properties of calix [5]arenes have been extensively investigated by diffraction, [1][2][3][4][5] organic synthesis [6][7][8][9][10] and computation methods. [11][12][13] The calix [5]arenes may posses a greater propensity to completely include small organic molecules than analogous calix [4]arenes due to their larger cavity size.…”

mentioning

confidence: 99%