Studies on Resorcinarenes and their Analytical Applications

Abstract

1) Where R, = Aliphatic or Aromatic groups R 2 = Η Resorcinarenes are interesting for their receptor properties and as building blocks for large supramolecular assemblies of a fascinating architecture /5,19-21/. The bridging of hydroxy 1 groups of resorcinarenes leads to cavitands, bowl shaped species serving as synthetic receptors and able to assembly into capsules 122-217.In this review, selected examples of resorcinarenes are described, showing their synthetic approaches and reactivity as well as formation of complexes, host-guest systems and capsules. The preparation of mono-and multi-layers of resorcinarenes, promising for their applications, is also presented. SYNTHESISResorcinarenes can be obtained in high yields via simple, one step procedures without using templates or high dilution techniques.A) Most cases involve the acid-catalyzed condensation reaction between resorcinol and aliphatic or aromatic aldehydes /10,11,28/.Weinelt and Schneider studied the reaction mechanism of the acidcatalyzed condensation reaction between resorcinol and acetaldehyde in methanol / HCl /29/.The electrophile stems not directly from the aldehyde but from its rapidly 156 Brought to you by | Purdue University Libraries Authenticated Download Date | 5/28/15 12:51 PM Y.K. Agrawal andR.N. Patadia Reviews in Analytical Chemistry 157 Brought to you by | Purdue University Libraries Authenticated Download Date | 5/28/15 12:51 PM Vol. 25, No. 3, 2006 Resorcinarenes and their Analytical ApplicationsThe ratio of the conformation of (10) is 3 : 2 mixture of boat isomer (all cis): diamond isomer ( cis.cis.trans).* Another high yield synthesis of resorcinarenes (13) involves the lewis acid catalyzed condensation tetramerization of 1,3-dimethoxy benzene (11) with isovalaraldehyde (12) /30/. Different types of lewis acids like SOCl 2 , POCl 3 , A1C1 3 , SiCl 2 Me 2 , SiClMe 3 , SnCl 4 had been used. Amongst these lewis acids, only SnCl 4 catalyses this reaction selectively and promotes the formation of the crown conformer (rccc) in high yield (85%).* When 2,4-dimethoxy benzyl alcohol (14) was treated with trifluoroacetic acid (5% in CHC1 3 ), resorcinarene (10) was obtained in 95 % yield /31/.The product is separated using reverse phase silica gel column HPLC.Measurements of steady state spectra and decay time of pyrene fluorescence of the (21) revealed that they form two types of excimer. * The synthesis of resorcinarene (22) was carried out by acid-catalyzed condensation of resorcinol with aldehydes, catalyzed by ytterbium (III) triflate nonahydrate {[Yb(H 2 0) 9 ](0Tf) 3 } /34/. * New ytterbium complexes with resorcinarene (121-127) containing methoxycarbonyl, methyldiethyl amino groups and bromine as the substituents in the resorcinol ring and methyl or phenyl substituents in the macroring were synthesized /85,86/.

Effect of the formation of capsules of tetra(propyl) pyrogallol[4]arene on the host-guest interaction with neurotransmitters

“…Interest in host-guest interaction using macrocyclic systems has increased in recent years. As an example, the use of macrocyclic ligands such as crown ethers 1 calixarenes 2,3 or resorcinarenes 4 for different analytical applications can be mentioned. In this field, the use of pyrogallol [4]arenes as macrocyclic molecules for molecular recognition has made a significant contribution to the development of new applications, including receptors for ammonium salts [5][6][7][8][9] , choline 10 , dopamine 11 , carnitine 12,13 , phosphocholine 14 , betaine 15 and pipecolinic acid among others 16,17 .…”

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Reaction between pyrogallol and butyraldehyde resulted in the formation of Ctetra(propyl)pyrogallol [4]arene and dimeric capsules. The structures were determined using FT-IR, 1 H-NMR, 13 C-NMR and mass spectrometry.

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“…The host-guest complex of C-tetra(propyl) pyrogallol[4]arene (1) and the capsule with neurotransmitters (choline, betaine and carnitine) were examined in DMSO via dynamic NMR and in the gas phase via electrospray ionization-mass spectrometry (ESI-MS). Initially, in DMSO, the results showed that the evaluated neurotransmitters formed a complex with C-tetra(propyl)pyrogallol [4]arene and with the capsule, which is broken by the interaction with the organic cation. Our careful NMR analysis was based on the assignment of 1 H-NMR signals of the C-tetra(propyl)pyrogallol [4]arene in DMSO-d6 after the addition of variable amounts of the respective neurotransmitter.…”

“…Initially, in DMSO, the results showed that the evaluated neurotransmitters formed a complex with C-tetra(propyl)pyrogallol [4]arene and with the capsule, which is broken by the interaction with the organic cation. Our careful NMR analysis was based on the assignment of 1 H-NMR signals of the C-tetra(propyl)pyrogallol [4]arene in DMSO-d6 after the addition of variable amounts of the respective neurotransmitter. With this solvent, it was possible to define stable cone conformational arrangements based on the signals shown in the spectra of all the experiments.…”

“…With this solvent, it was possible to define stable cone conformational arrangements based on the signals shown in the spectra of all the experiments. Association constants (K) of pyrogallo [4]arene with the neurotransmitters were estimated, and the results showed that betaine complex had the highest K value. In the gasphase study using ESI-MS, the results showed the formation of a 1:1 inclusion complex between the studied neurotransmitters and pyrogallo[4]arene.…”