Host–Guest Interactions in ExBox⁴⁺

Abstract

The host-guest interaction between benzene/ azine with the newly synthesized

Shedding Light on the Nature of Host–Guest Interactions in PAHs-ExBox4+ Complexes

“…This amplified molecular recognition is possible due to the electronic structure of Ex 2 Box 4+ , which comprises two pyridinium rings located at the edge of the cyclophane, which form donoracceptor interactions with π-electron-rich guests, while the spacers (biphenylene), located between the pyridinium rings, are more electron-rich and prefer to interact with π-electronpoor guests. 22,28 DFT calculations [21][22][23][24][25][26][27][28] have been extensively employed to evaluate the geometries, elec- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 still limited. Recently, Bachrach 30,31 studied the binding free energy of some linear acenes in 1 using different DFT functionals, and on attempt to understand ring strain and electrostatic influence at complex structures, Bachrach also design a neutral analogue of ExBox 4+ , giving the idea that electrostatics contribution account for 10-20% of the total binding energy.…”

“…For that reason, different sort of compounds, able to recognize PAHs such as cyclodextrins, − calix­[n]­arenes, − colic acid, and diazapyrenium-based metallocycles, , have been extensively synthesized. Recently, Stoddart and co-workers − reported the preparation, solid-state characterization, and HG binding affinities of a semirigid family of tetracationic cyclophanes, named ExBox 4+ ( 1 ), which are constituted by two π-electron-poor 4,4′-bipyridinium units tethered by two p -xylylene linkers (Figure a). Stoddart and co-workers have described the ability of 1 to scavenge 11 different electron-rich PAHs (azulene ( 2 ), anthracene ( 3 ), phenanthrene ( 4 ), pyrene ( 5 ), tetracene ( 6 ), tetraphene ( 7 ), chrysene ( 8 ), helicene ( 9 ), triphenylene ( 10 ), perylene ( 11 ), and coronene ( 12 ); Figure b) in different environments, observing that all PAHs ( 2 - 12 ) form inclusion complexes (PAHs⊂ExBox 4+ ) ( 2 ⊂ 1 - 12 ⊂ 1 ) with ExBox 4+ (Figure S1).…”

“…The extended version of 1 , the Ex 2 Box 4+ was also identified to be able to bind with π-electron-rich and -poor guests. This amplified molecular recognition is possible due to the electronic structure of Ex 2 Box 4+ , which comprises two pyridinium rings located at the edge of the cyclophane, which form donor–acceptor interactions with π-electron-rich guests, while the spacers (biphenylene), located between the pyridinium rings, are more electron-rich and prefer to interact with π-electron-poor guests. , …”

The ability of Ex2Box4+ to interact with guests containing π‐electron‐rich and π‐electron‐poor moieties

“…Das and coworkers also studied the HG interaction between 1 and PAHs, and reported that 1 becomes a more efficient absorber of hydrogen and carbon monoxide, with a significant rate of storage when interacting with lithium ions . Bachrach reported the binding energies between 1 and linear acenes, describing the conformational behavior of 1 , as well as the effects related with the size of guests as anthracene and tetracene.…”

Does Confinement Always Lead to Thermodynamically and/or Kinetically Favorable Reactions? A Case Study using Diels–Alder Reactions within ExBox+4and CB[7]

“…[1][2][3][4][5][6][7][8] Various organic host molecules provide ideal platformst oe ncapsulate an atom or am olecule and therebyt os tudy the effects of confinemento n the reactivity patterns of the associated guest. [6][7][8][9][10][11][12][13] It could be expected that the encapsulation of am olecule inside a" container" would lead to significantly altered electronic density distribution of the guest as compared with that of the free analogue;i nm any such situations, an enhancement of reactivity of the guest would occur.O ne important application of this could be in the design of highly efficient reaction vessels in organic chemistry. Indeed, in contemporary organic chemistry, immense efforts have been devoted to the field of supramolecular catalysis.…”