Synthesis of Electron‐Deficient Corona[5]arenes and Their Selective Complexation with Dihydrogen Phosphate: Cooperative Effects of Anion–π Interactions

Abstract

Reported here are the syntheses, conformational structures, electrochemical properties, and noncovalent anion binding of corona[5]arenes. A (3+2) fragment coupling reaction proceeded efficiently under mild reaction conditions to produce a number of novel heteroatom‐ and methylene‐bridged corona[3]arene[2]tetrazine macrocycles. Selective oxidation of the sulfur atom between two phenylene rings afforded sulfoxide‐ and sulfone‐linked corona[5]arenes in good yields. All corona[5]arenes synthesized adopted similar 1,2,4‐alternate conformational structures, forming pentagonal cavities. The cavity sizes and the electronic properties such as redox potentials, were measured with CV and DPV, and were influenced by the different bridging units. As electron‐deficient macrocycles, the acquired corona[3]arene[2]tetrazines served as highly selective hosts, forming complexes with the hydrogen‐bonded dimer of dihydrogen phosphate through cooperative anion–π interactions.

Synthesis ofi‐Corona[6]arenes for Selective Anion Binding: Interdependent and Synergistic Anion–π and Hydrogen‐Bond Interactions

“…It does not interact with other anions such as triangular nitrate either. It is most probably due to the macrocyclic conformation and the large cavity which are not suitable to include an anion by forming multiple anion–π interactions [30, 31, 33, 34] . Learning the lessons from our previous studies, we now design a novel type of multidentate macrocycles, i ‐corona[3]arene[3]tetrazines 3 (Figure 1).…”

“…[14,17] Thea nion-p interactions in complexation of oxacalix [2]arene [2]triazine derivatives with anions have also been demonstrated successfully in the fabrication of assembled structures, [23,24] responsive vesicles [23] and anion sensing systems. [22,28] Seeking for anion receptors which would also serve as the potential building units for the construction of artificial anion channels,wehave recently devised coronarenes, [29][30][31][32][33][34] anew type of macrocyclic compounds.C onstituted by para-(het)arylenes and heteroatoms in an alternative manner, coronarenes adopt coronary conformation with cylindroid cavities.F or example,O 6corona [3]arene [3]tetrazine 2 ( Figure 1) gives ar egular hexagonal structure with three tetrazine rings and six oxygen atom linkages form almost aplane while the three phenylene Figure 1. General structure of tetraoxacalix [2]arene [2]triazine 1,O 6corona [3]arene [3]tetrazine 2 and i-corona [3]arene [3] rings are nearly perpendicular to the plane.A sa ne lectrondeficient macrocycle,O 6 -corona [3]arene [3]tetrazinec omplexes with chlorides via anion-p interactions.…”

“…[30] It does not interact with other anions such as triangular nitrate either.Itismost probably due to the macrocyclic conformation and the large cavity which are not suitable to include an anion by forming multiple anion-p interactions. [30,31,33,34] Learning the lessons from our previous studies,w en ow design an ovel type of multidentate macrocycles, i-corona [3]arene [3]tetrazines 3 ( Figure 1). We reasoned that our newly designed macrocycles would adopt different macrocyclic conformational structures with asmaller cavity in comparison to corona [3]arene [3]tetrazines 2 because of the variation of the substitution pattern of phenylenes.The cavity formed by three electron-deficient tetrazine rings would confer cooperative anion-p binding power on macrocycles 3.P articularly, i-corona [3]arene [3]tetrazines would display great selectivity to bind triangular nitrate,a na nion which plays significant roles in life science and in environment, [35,36] owing to the perfect complementary electronic and steric effects between host and guest.…”

Synthesis ofi‐Corona[6]arenes for Selective Anion Binding: Interdependent and Synergistic Anion–π and Hydrogen‐Bond Interactions

“…The anion‐π interactions in complexation of oxacalix[2]arene[2]triazine derivatives with anions have also been demonstrated successfully in the fabrication of assembled structures, [23, 24] responsive vesicles [23] and anion sensing systems [22, 28] . Seeking for anion receptors which would also serve as the potential building units for the construction of artificial anion channels, we have recently devised coronarenes, [29–34] a new type of macrocyclic compounds. Constituted by para ‐(het)arylenes and heteroatoms in an alternative manner, coronarenes adopt coronary conformation with cylindroid cavities.…”

Dynamic Nucleophilic Aromatic Substitution of Tetrazines

“…[ 47 , 48 , 49 , 50 , 51 ] Tetrazine is a valuable scaffold to build stimulating architectures such as corona[ n ]arenes. [ 52 , 53 , 54 , 55 , 56 , 57 ] They also show an interesting redox performance,[ 58 , 59 , 60 ] and some of them display fluorescence. [ 61 , 62 , 63 , 64 ] Even when it is known that some tetrazines, such as 3,6‐dichloro‐1,2,4,5‐tetrazine ( Cl‐Tz‐Cl ) can undergo S N Ar,[ 65 , 66 ] the reversibility of the substitution is completely unexplored.…”