A General Synthesis of Macrocyclic π-Electron-Acceptor Systems

Abstract

Cyclocondensations of aromatic diamines with 1,1'-bis(2,4-dinitrophenyl)-4,4'-bipyridinium salts afford doubly or quadruply charged, macrocyclic, N,N'-diarylbipyridinium cations. These are tolerant of a wide range of acids, bases, and nucleophiles, although they appear to undergo reversible, one-electron reduction by tertiary amines. Single-crystal X-ray analysis demonstrates the presence of a macrocycle conformation in which the 4,4'-bipyridinium and 4,4'-biphenylenedisulfonyl residues are suitably spaced and aligned for complexation with pi-donor arenes, and NMR studies in solution indeed confirm binding to 1,5-bis[hydroxy(ethoxy)ethoxy]naphthalene.

Efficient access to conjugated 4,4′-bipyridinium oligomers using the Zincke reaction: synthesis, spectroscopic and electrochemical properties

“…We next studied the chemically reversible redox process using TEA and trifluoroacetic acid (TFA), as described previously for the macrocyclic systems. 60 Fig. 2(A) shows the 1 H NMR spectrum of an orange solution of trimer 3, which exhibits clearly resolved signals in the aromatic region (7.5 to 10.0 ppm), as well as two distinct resonances from the methoxy-ether and methoxy-ester residues (3.8 and 4.0 ppm).…”

Mutual Complexation between π–π Stacked Molecular Tweezers

“…21 However, as noted by Hunter and Sanders, charge transfer in this situation is a consequence, rather than a cause, of complementary - stacking. We ourselves have previously reported diimide-based macrocycles 22,23 which allow the self-assembly of complementary "smallmolecule" - stacked motifs, as well as polymer blends in which supramolecular -stacking results in the formation of self-assembled and intrinsically healable materials. [24][25][26][27][28][29][30][31][32][33][34][35][36] Earlier computational studies 37 predicted that two π-electron deficient naphthalene diimide moieties separated by a flexible linker derived from 2,2'-(ethylenedioxy)bis(ethylamine), and with simple Nmethyl substituents as the terminal units (for ease of computation), should give rise to a chain-folding motif that would exhibit complementary face-to-face π-π stacking interactions with a π-electron rich, pyrenyl tweezer-molecule ( Figure 1).…”

Flexible Viologen Cyclophanes: Odd/Even Effects on Intramolecular Interactions

“…[18] Synthetic yields were low,u naffected by the use of templatesa nd surprisingly sensitivet ow hether the intended alkyl linkers contained an odd or even number of carbon atoms. An alternative synthetic approachu sing the Zincke reaction [19,20] was designed according to the assumption that the use of an electron-rich template would be most efficient if applied to the cyclization of at etracationic bis-viologenc lip (5 4 + )r ather than to ap artially quaternized bipyridine intermediate such as 4 2 + (Scheme 1). An alternative synthetic approachu sing the Zincke reaction [19,20] was designed according to the assumption that the use of an electron-rich template would be most efficient if applied to the cyclization of at etracationic bis-viologenc lip (5 4 + )r ather than to ap artially quaternized bipyridine intermediate such as 4 2 + (Scheme 1).…”

“…Cyclophanes with an even number of carbon atoms in the linkersw ere not produced by this method. An alternative synthetic approachu sing the Zincke reaction [19,20] was designed according to the assumption that the use of an electron-rich template would be most efficient if applied to the cyclization of at etracationic bis-viologenc lip (5 4 + )r ather than to ap artially quaternized bipyridine intermediate such as 4 2 + (Scheme 1). Te trathiafulvalene (TTF) was selected as apossible template because it forms ag reen charge-transfer complex with the larger cyclophane 3(PF 6 ) 4 .D espite the low binding constant( K a = 21 AE1 m À1 in MeCN, see the Supporting Information) of 3 with TTF,w er easoned that bindingm ight be stronger with 2(PF 6 ) 4 ,w hich should have as maller cavity than 3(PF 6 ) 4 .T og enerate ab is-viologen clip, the hexyl-linked bis(pyridinium-pyridine) [21] 4 2 + was treated with 2,4-dinitrochlorobenzene in MeCN at reflux (Scheme1)t og ive the Zincke salt 5 4 + in 81 %y ield.…”