A Radically Configurable Six-State Compound

Most organic radicals possess short lifetimes and quickly undergo dimerization or oxidation. Here, we report on the synthesis by radical templation of a class of air- and water-stable organic radicals, trapped within a homo[2]catenane composed of two rigid and fixed cyclobis (paraquat-p-phenylene) rings. The highly energetic octacationic homo[2]catenane, which is capable of accepting up to eight electrons, can be configured reversibly, both chemically and electrochemically, between each one of six experimentally accessible redox states (0, 2+, 4+, 6+, 7+, and 8+) from within the total of nine states evaluated by quantum mechanical methods. All six of the observable redox states have been identified by electrochemical techniques, three (4+, 6+, and 7+) have been characterized by x-ray crystallography, four (4+, 6+, 7+, and 8+) by electron paramagnetic resonance spectroscopy, one (7+) by superconducting quantum interference device magnetometry, and one (8+) by nuclear magnetic resonance spectroscopy

ExBox: a polycyclic aromatic hydrocarbon scavenger

A template-directed protocol, which capitalizes on donor acceptor interactions, is employed to synthesize a semi-rigid cyclophane (ExBox(4+)) that adopts a box-like geometry and is comprised of pi-electron-poor 1,4-phenylene-bridged ("extended") bipyridinium units (ExBIPY(2+)). ExBox(4+) functions as a high-affinity scavenger of an array of different polycyclic aromatic hydrocarbons (PAHs), ranging from two to seven fused rings, as a result of its large, accommodating cavity (approximately 3.5 angstrom in width and 11.2 angstrom in length when considering the van der Waals radii) and its ability to form strong non-covalent bonding interactions with pi-electron-rich PAHs in either organic or aqueous media. In all, 11 PAH guests were observed to form inclusion complexes with ExBox(4+), with coronene being the largest included guest. Single-crystal X-ray diffraction data for the 11 inclusion complexes EaBox(4+)subset of PAH as well as UV/vis spectroscopic data for 10 of the complexes provide evidence of the promiscuity of ExBox(4+) for the various PAHs. Nuclear magnetic resonance spectroscopy and isothermal titration calorimetric analyses of 10 of the inclusion complexes are employed to further characterize the host guest interactions in solution and determine the degree with which ExBox(4+) binds each PAR compound. As a proof-of-concept, a batch of crude oil from Saudi Arabia was subjected to extraction with the water-soluble form of the PAH receptor, ExBox center dot 4Cl, resulting in the isolation of different aromatic compounds after ExBox center dot 4Cl was regenerated.A template-directed protocol, which capitalizes on donor− acceptor interactions, is employed to synthesize a semi-rigid cyclophane (ExBox4+) that adopts a box-like geometry and is comprised of π-electronpoor 1,4-phenylene-bridged (“extended”) bipyridinium units (ExBIPY2+). ExBox4+ functions as a high-affinity scavenger of an array of different polycyclic aromatic hydrocarbons (PAHs), ranging from two to seven fused rings, as a result of its large, accommodating cavity (approximately 3.5 Å in width and 11.2 Å in length when considering the van der Waals radii) and its ability to form strong non-covalent bonding interactions with π-electron-rich PAHs in either organic or aqueous media. In all, 11 PAH guests were observed to form inclusion complexes with ExBox4+, with coronene being the largest included guest. Single-crystal X-ray diffraction data for the 11 inclusion complexes ExBox4+⊂PAH as well as UV/vis spectroscopic data for 10 of the complexes provide evidence of the promiscuity of ExBox4+ for the various PAHs. Nuclear magnetic resonance spectroscopy and isothermal titration calorimetric analyses of 10 of the inclusion complexes are employed to further characterize the host−guest interactions in solution and determine the degree with which ExBox4+ binds each PAH compound. As a proof of-concept, a batch of crude oil from Saudi Arabia was subjected to extraction with the water-soluble form of the PAH receptor, ExBox·4Cl, resulting in the isolation of different aromatic compounds after ExBox·4Cl was regenerated

Mechanically induced intramolecular electron transfer in a mixed-valence molecular shuttle

The kinetics and thermodynamics of intramolecular electron transfer (IET) can be subjected to redox control in a bistable [2] rotaxane comprised of a dumbbell component containing an electron-rich 1,5-dioxynaphthalene (DNP) unit and an electron-poor phenylene-bridged bipyridinium (P-BIPY2+) unit and a cyclobis (paraquat-p-phenylene) (CBPQT(4+)) ring component. The [2] rotaxane exists in the ground-state co-conformation (GSCC) wherein the CBPQT(4+) ring encircles the DNP unit. Reduction of the CBPQT(4+) leads to the CBPQT(2(center dot+)) diradical dication while the P-BIPY2+ unit is reduced to its P-BIPY center dot+ radical cation. A radical-state co-conformation (RSCC) results from movement of the CBPQT(2(center dot+)) ring along the dumbbell to surround the P-BIPY center dot+ unit. This shuttling event induces IET to occur between the pyridinium redox centers of the P-BIPY center dot+ unit, a property which is absent between these redox centers in the free dumbbell and in the 1:1 complex formed between the CBPQT(2(center dot+)) ring and the radical cation of methyl-phenylene-viologen (MPV center dot+). Using electron paramagnetic resonance (EPR) spectroscopy, the process of IET was investigated by monitoring the line broadening at varying temperatures and determining the rate constant (k(ET) 1.33 x 10(7) s(-1)) and activation energy (Delta G double dagger = 1.01 kcal mol(-1)) for electron transfer. These values were compared to the corresponding values predicted, using the optical absorption spectra and Marcus-Hush theory.The kinetics and thermodynamics of intramolecular electron transfer (IET) can be subjected to redox control in a bistable [2] rotaxane comprised of a dumbbell component containing an electron-rich 1,5-dioxynaphthalene (DNP) unit and an electron-poor phenylene-bridged bipyridinium (P-BIPY2+) unit and a cyclobis (paraquat-p-phenylene) (CBPQT(4+)) ring component. The [2] rotaxane exists in the ground-state co-conformation (GSCC) wherein the CBPQT(4+) ring encircles the DNP unit. Reduction of the CBPQT(4+) leads to the CBPQT(2(center dot+)) diradical dication while the P-BIPY2+ unit is reduced to its P-BIPY center dot+ radical cation. A radical-state co-conformation (RSCC) results from movement of the CBPQT(2(center dot+)) ring along the dumbbell to surround the P-BIPY center dot+ unit. This shuttling event induces IET to occur between the pyridinium redox centers of the P-BIPY center dot+ unit, a property which is absent between these redox centers in the free dumbbell and in the 1:1 complex formed between the CBPQT(2(center dot+)) ring and the radical cation of methyl-phenylene-viologen (MPV center dot+). Using electron paramagnetic resonance (EPR) spectroscopy, the process of IET was investigated by monitoring the line broadening at varying temperatures and determining the rate constant (k(ET) 1.33 x 10(7) s(-1)) and activation energy (Delta G double dagger = 1.01 kcal mol(-1)) for electron transfer. These values were compared to the corresponding values predicted, using the optical absorption spectra and Marcus-Hush theory

ExBox: A Polycyclic Aromatic Hydrocarbon Scavenger

A template-directed protocol, which capitalizes on donor–acceptor interactions, is employed to synthesize a semi-rigid cyclophane (<b>ExBox</b>⁴⁺) that adopts a box-like geometry and is comprised of π-electron-poor 1,4-phenylene-bridged (“extended”) bipyridinium units (<b>ExBIPY</b>²⁺). <b>ExBox</b>⁴⁺ functions as a high-affinity scavenger of an array of different polycyclic aromatic hydrocarbons (PAHs), ranging from two to seven fused rings, as a result of its large, accommodating cavity (approximately 3.5 Å in width and 11.2 Å in length when considering the van der Waals radii) and its ability to form strong non-covalent bonding interactions with π-electron-rich PAHs in either organic or aqueous media. In all, 11 PAH guests were observed to form inclusion complexes with <b>ExBox</b>⁴⁺, with coronene being the largest included guest. Single-crystal X-ray diffraction data for the 11 inclusion complexes <b>ExBox</b>⁴⁺⊂PAH as well as UV/vis spectroscopic data for 10 of the complexes provide evidence of the promiscuity of <b>ExBox</b>⁴⁺ for the various PAHs. Nuclear magnetic resonance spectroscopy and isothermal titration calorimetric analyses of 10 of the inclusion complexes are employed to further characterize the host–guest interactions in solution and determine the degree with which <b>ExBox</b>⁴⁺ binds each PAH compound. As a proof-of-concept, a batch of crude oil from Saudi Arabia was subjected to extraction with the water-soluble form of the PAH receptor, <b>ExBox</b>·4Cl, resulting in the isolation of different aromatic compounds after <b>ExBox</b>·4Cl was regenerated

ExBox: A Polycyclic Aromatic Hydrocarbon Scavenger

A template-directed protocol, which capitalizes on donor–acceptor interactions, is employed to synthesize a semi-rigid cyclophane (<b>ExBox</b>⁴⁺) that adopts a box-like geometry and is comprised of π-electron-poor 1,4-phenylene-bridged (“extended”) bipyridinium units (<b>ExBIPY</b>²⁺). <b>ExBox</b>⁴⁺ functions as a high-affinity scavenger of an array of different polycyclic aromatic hydrocarbons (PAHs), ranging from two to seven fused rings, as a result of its large, accommodating cavity (approximately 3.5 Å in width and 11.2 Å in length when considering the van der Waals radii) and its ability to form strong non-covalent bonding interactions with π-electron-rich PAHs in either organic or aqueous media. In all, 11 PAH guests were observed to form inclusion complexes with <b>ExBox</b>⁴⁺, with coronene being the largest included guest. Single-crystal X-ray diffraction data for the 11 inclusion complexes <b>ExBox</b>⁴⁺⊂PAH as well as UV/vis spectroscopic data for 10 of the complexes provide evidence of the promiscuity of <b>ExBox</b>⁴⁺ for the various PAHs. Nuclear magnetic resonance spectroscopy and isothermal titration calorimetric analyses of 10 of the inclusion complexes are employed to further characterize the host–guest interactions in solution and determine the degree with which <b>ExBox</b>⁴⁺ binds each PAH compound. As a proof-of-concept, a batch of crude oil from Saudi Arabia was subjected to extraction with the water-soluble form of the PAH receptor, <b>ExBox</b>·4Cl, resulting in the isolation of different aromatic compounds after <b>ExBox</b>·4Cl was regenerated

ExBox: A Polycyclic Aromatic Hydrocarbon Scavenger

A template-directed protocol, which capitalizes on donor–acceptor interactions, is employed to synthesize a semi-rigid cyclophane (<b>ExBox</b>⁴⁺) that adopts a box-like geometry and is comprised of π-electron-poor 1,4-phenylene-bridged (“extended”) bipyridinium units (<b>ExBIPY</b>²⁺). <b>ExBox</b>⁴⁺ functions as a high-affinity scavenger of an array of different polycyclic aromatic hydrocarbons (PAHs), ranging from two to seven fused rings, as a result of its large, accommodating cavity (approximately 3.5 Å in width and 11.2 Å in length when considering the van der Waals radii) and its ability to form strong non-covalent bonding interactions with π-electron-rich PAHs in either organic or aqueous media. In all, 11 PAH guests were observed to form inclusion complexes with <b>ExBox</b>⁴⁺, with coronene being the largest included guest. Single-crystal X-ray diffraction data for the 11 inclusion complexes <b>ExBox</b>⁴⁺⊂PAH as well as UV/vis spectroscopic data for 10 of the complexes provide evidence of the promiscuity of <b>ExBox</b>⁴⁺ for the various PAHs. Nuclear magnetic resonance spectroscopy and isothermal titration calorimetric analyses of 10 of the inclusion complexes are employed to further characterize the host–guest interactions in solution and determine the degree with which <b>ExBox</b>⁴⁺ binds each PAH compound. As a proof-of-concept, a batch of crude oil from Saudi Arabia was subjected to extraction with the water-soluble form of the PAH receptor, <b>ExBox</b>·4Cl, resulting in the isolation of different aromatic compounds after <b>ExBox</b>·4Cl was regenerated

ExBox: A Polycyclic Aromatic Hydrocarbon Scavenger

A template-directed protocol, which capitalizes on donor–acceptor interactions, is employed to synthesize a semi-rigid cyclophane (<b>ExBox</b>⁴⁺) that adopts a box-like geometry and is comprised of π-electron-poor 1,4-phenylene-bridged (“extended”) bipyridinium units (<b>ExBIPY</b>²⁺). <b>ExBox</b>⁴⁺ functions as a high-affinity scavenger of an array of different polycyclic aromatic hydrocarbons (PAHs), ranging from two to seven fused rings, as a result of its large, accommodating cavity (approximately 3.5 Å in width and 11.2 Å in length when considering the van der Waals radii) and its ability to form strong non-covalent bonding interactions with π-electron-rich PAHs in either organic or aqueous media. In all, 11 PAH guests were observed to form inclusion complexes with <b>ExBox</b>⁴⁺, with coronene being the largest included guest. Single-crystal X-ray diffraction data for the 11 inclusion complexes <b>ExBox</b>⁴⁺⊂PAH as well as UV/vis spectroscopic data for 10 of the complexes provide evidence of the promiscuity of <b>ExBox</b>⁴⁺ for the various PAHs. Nuclear magnetic resonance spectroscopy and isothermal titration calorimetric analyses of 10 of the inclusion complexes are employed to further characterize the host–guest interactions in solution and determine the degree with which <b>ExBox</b>⁴⁺ binds each PAH compound. As a proof-of-concept, a batch of crude oil from Saudi Arabia was subjected to extraction with the water-soluble form of the PAH receptor, <b>ExBox</b>·4Cl, resulting in the isolation of different aromatic compounds after <b>ExBox</b>·4Cl was regenerated

ExBox: A Polycyclic Aromatic Hydrocarbon Scavenger

A template-directed protocol, which capitalizes on donor–acceptor interactions, is employed to synthesize a semi-rigid cyclophane (<b>ExBox</b>⁴⁺) that adopts a box-like geometry and is comprised of π-electron-poor 1,4-phenylene-bridged (“extended”) bipyridinium units (<b>ExBIPY</b>²⁺). <b>ExBox</b>⁴⁺ functions as a high-affinity scavenger of an array of different polycyclic aromatic hydrocarbons (PAHs), ranging from two to seven fused rings, as a result of its large, accommodating cavity (approximately 3.5 Å in width and 11.2 Å in length when considering the van der Waals radii) and its ability to form strong non-covalent bonding interactions with π-electron-rich PAHs in either organic or aqueous media. In all, 11 PAH guests were observed to form inclusion complexes with <b>ExBox</b>⁴⁺, with coronene being the largest included guest. Single-crystal X-ray diffraction data for the 11 inclusion complexes <b>ExBox</b>⁴⁺⊂PAH as well as UV/vis spectroscopic data for 10 of the complexes provide evidence of the promiscuity of <b>ExBox</b>⁴⁺ for the various PAHs. Nuclear magnetic resonance spectroscopy and isothermal titration calorimetric analyses of 10 of the inclusion complexes are employed to further characterize the host–guest interactions in solution and determine the degree with which <b>ExBox</b>⁴⁺ binds each PAH compound. As a proof-of-concept, a batch of crude oil from Saudi Arabia was subjected to extraction with the water-soluble form of the PAH receptor, <b>ExBox</b>·4Cl, resulting in the isolation of different aromatic compounds after <b>ExBox</b>·4Cl was regenerated

ExBox: A Polycyclic Aromatic Hydrocarbon Scavenger

A template-directed protocol, which capitalizes on donor–acceptor interactions, is employed to synthesize a semi-rigid cyclophane (<b>ExBox</b>⁴⁺) that adopts a box-like geometry and is comprised of π-electron-poor 1,4-phenylene-bridged (“extended”) bipyridinium units (<b>ExBIPY</b>²⁺). <b>ExBox</b>⁴⁺ functions as a high-affinity scavenger of an array of different polycyclic aromatic hydrocarbons (PAHs), ranging from two to seven fused rings, as a result of its large, accommodating cavity (approximately 3.5 Å in width and 11.2 Å in length when considering the van der Waals radii) and its ability to form strong non-covalent bonding interactions with π-electron-rich PAHs in either organic or aqueous media. In all, 11 PAH guests were observed to form inclusion complexes with <b>ExBox</b>⁴⁺, with coronene being the largest included guest. Single-crystal X-ray diffraction data for the 11 inclusion complexes <b>ExBox</b>⁴⁺⊂PAH as well as UV/vis spectroscopic data for 10 of the complexes provide evidence of the promiscuity of <b>ExBox</b>⁴⁺ for the various PAHs. Nuclear magnetic resonance spectroscopy and isothermal titration calorimetric analyses of 10 of the inclusion complexes are employed to further characterize the host–guest interactions in solution and determine the degree with which <b>ExBox</b>⁴⁺ binds each PAH compound. As a proof-of-concept, a batch of crude oil from Saudi Arabia was subjected to extraction with the water-soluble form of the PAH receptor, <b>ExBox</b>·4Cl, resulting in the isolation of different aromatic compounds after <b>ExBox</b>·4Cl was regenerated