Herein we report two ruthenium benzylidene complexes with benzylphosphite ligands for olefin meta... more Herein we report two ruthenium benzylidene complexes with benzylphosphite ligands for olefin metathesis. Unlike the previously reported benzylidene phosphite complexes, the benzylphosphite complexes adopt a cis-dichloro con-figuration making them latent at ambient temperatures. Irradiation with visible light (420 nm and blue LED) prompts activation of the complexes and induces catalysis of olefin metathesis reactions. One of the complexes, cis-Ru-1, was found especially suitable for 3D printing of multilayered polydicyclopentadiene structures with excellent spatial reso-lutions. Additionally, complex cis-Ru-2 was designed with a chromatic orthogonal 'kill switch' based on the 2-nitrobenzyl chemistry, allowing the destruction of the catalyst upon exposure to UVC light.
Four new cis-dianionic S-chelated ruthenium benzylidenes were synthesized by chloride ligand exch... more Four new cis-dianionic S-chelated ruthenium benzylidenes were synthesized by chloride ligand exchange. The special cis-dianionic conformation of these complexes contributed to a particularly facile anion exchange process, producing room-temperature-latent precatalysts. Their catalytic activity was strongly influenced by the solvent used. The latent iodide complex very efficiently promoted ring-closing metathesis by heating in toluene. Conversely, carboxylate ligands produced quite poor catalysts, but could abstract chlorides from chlorinated solvents to transform into active precatalysts. In tetrahydrofuran (THF), the S-chelated dichloro complex was shown to promote cycloisomerization instead of metathesis; however, the metathesis activity in THF could be recovered in the presence of phenylacetylene as a cocatalyst. Under the same conditions, all the other complexes required addition of LiCl to mimic this dichotomous behavior.
The title compound, C46H26N2O7@1.5CH3CN, is the aldol condensation product of bindone with indazo... more The title compound, C46H26N2O7@1.5CH3CN, is the aldol condensation product of bindone with indazole-3-carbaldehyde followed by double intermolecular cyclization. The asymmetric unit, which has monoclinic P2 1 /c symmetry, contains two independent molecules of the title compound and three acetonitrile molecules. The title molecule comprises a central eight-membered ring, which contains an enol-ester, from which five arms extend. The arms exhibit intermolecular interactions within the crystal lattice between molecules of the title compound and with co-crystallized solvent molecules (acetonitrile).
Crystallization‐induced emission (CIE) has been reported for a handful of polyaromatic molecules,... more Crystallization‐induced emission (CIE) has been reported for a handful of polyaromatic molecules, and this phenomenon has been generally ascribed to blocking of nonradiative energy dissipation pathways through crystalline organizations. Herein, the first use of a single‐ring CIE‐based “invisible” ink is reported, which can be applied on varied surfaces. The ink comprises (3E)‐4‐[4‐(methylsulfanyl)phenyl]‐3‐buten‐2‐one (MSPB), exhibiting remarkable spontaneous water and interface‐induced CIE. The molecule, which is synthesized through a facile one‐step process, is nonfluorescent when dissolved in polar organic solvents but forms fluorescent crystalline assemblies upon addition of water or upon drying on solid substrates. X‐ray diffraction analysis reveals that the fluorescent crystalline structure of MSPB is stabilized both by intermolecular C⋅⋅⋅HO and C⋅⋅⋅Hπ interactions among adjacent molecules. The readily adopted crystalline organization of MSPB facilitates its use as a fluorescent ink on diverse substrates, including paper, metals, polymers, and ceramic surfaces. Crystallization‐induced emission (CIE) of a molecule displaying a single phenyl ring is reported. The fluorescence emission is ascribed to the crystalline organization of the molecule, blocking π–π stacking and concomitant nonradiative energy dissipation. The CIE phenomenon is exploited for utilizing the molecule as an “invisible ink” on a variety of surfaces.
Alcohols, with hydroxyl groups compositionally identical to water itself, are consummate hydrophi... more Alcohols, with hydroxyl groups compositionally identical to water itself, are consummate hydrophiles, whose high solubilities preclude spontaneous self-assembly in water. Nevertheless, the solute-solvent interactions associated with their highly favorable solvation enthalpies impose substantial entropic costs, similar in magnitude to those that drive the hydrophobic assembly of alkanes. We now show that under nanoconfined conditions this normally dormant "hydrophobicity" can emerge as the driving force for alcohol encapsulation. Using a porous molecular capsule, the displacement of endohedrally coordinated formate ligands (HCO2-) by 1,2-hydroxyl-functionalized l-glycerate (l-gly, l-HOCH2(HO)CHCO2-) was investigated by van't Hoff analysis of variable-temperature 1H NMR in D2O. At pD 5.8, l-gly uptake is enthalpically inhibited. Upon attenuation of this unfavorable change in enthalpy by cosequestration of protons within the alcoholic environment provided by encapsulated diol-functionalized ligands, - TΔ S° dominates over Δ H°, spontaneously filling the capsule to its host capacity of 24 l-gly ligands via an entropically driven hydrophobic response.
While sophisticated computational methods can predict 31P NMR spectra of phosphorus atoms encapsu... more While sophisticated computational methods can predict 31P NMR spectra of phosphorus atoms encapsulated within Keggin-derived heteropoly tungstate and molybdate cluster anions, calculated and experimental chemical shift values typically deviate considerably from one another. Motivated by the observation that experimentally determined 31P chemical shift values within a series of water-soluble plenary and metal-cation substituted lacunary Keggin anions, [PMnW11O39](7–n)– (Mn = Ag+, Zn2+, Nb5+, W6+) and [(PW11O39)2Mn](14–n)– (Mn = Y3+, Zr4+), varied as a linear function of the oxidation states, n, of the complexed Mn cations, a linear correlation was sought between observed chemical shift values and the net Coulombic forces experienced by the encapsulated phosphorus atoms. The Coulombic model based on Shannon radii, published electronegativity values, and bond angles from X-ray crystallographic data remarkably accounted for the relative 31P chemical shift values of phosphorus atoms in over 50 metal-oxide cluster anions, including large structures comprised of up to four Keggin-derived fragments with an overall R2 value of 0.974. With the model being applied here to three cluster anions whose 31P chemical shift values are reported here for the first time, predicted and experimental values differed by only ±0.4 ppm.
Herein we report two ruthenium benzylidene complexes with benzylphosphite ligands for olefin meta... more Herein we report two ruthenium benzylidene complexes with benzylphosphite ligands for olefin metathesis. Unlike the previously reported benzylidene phosphite complexes, the benzylphosphite complexes adopt a cis-dichloro con-figuration making them latent at ambient temperatures. Irradiation with visible light (420 nm and blue LED) prompts activation of the complexes and induces catalysis of olefin metathesis reactions. One of the complexes, cis-Ru-1, was found especially suitable for 3D printing of multilayered polydicyclopentadiene structures with excellent spatial reso-lutions. Additionally, complex cis-Ru-2 was designed with a chromatic orthogonal 'kill switch' based on the 2-nitrobenzyl chemistry, allowing the destruction of the catalyst upon exposure to UVC light.
Four new cis-dianionic S-chelated ruthenium benzylidenes were synthesized by chloride ligand exch... more Four new cis-dianionic S-chelated ruthenium benzylidenes were synthesized by chloride ligand exchange. The special cis-dianionic conformation of these complexes contributed to a particularly facile anion exchange process, producing room-temperature-latent precatalysts. Their catalytic activity was strongly influenced by the solvent used. The latent iodide complex very efficiently promoted ring-closing metathesis by heating in toluene. Conversely, carboxylate ligands produced quite poor catalysts, but could abstract chlorides from chlorinated solvents to transform into active precatalysts. In tetrahydrofuran (THF), the S-chelated dichloro complex was shown to promote cycloisomerization instead of metathesis; however, the metathesis activity in THF could be recovered in the presence of phenylacetylene as a cocatalyst. Under the same conditions, all the other complexes required addition of LiCl to mimic this dichotomous behavior.
The title compound, C46H26N2O7@1.5CH3CN, is the aldol condensation product of bindone with indazo... more The title compound, C46H26N2O7@1.5CH3CN, is the aldol condensation product of bindone with indazole-3-carbaldehyde followed by double intermolecular cyclization. The asymmetric unit, which has monoclinic P2 1 /c symmetry, contains two independent molecules of the title compound and three acetonitrile molecules. The title molecule comprises a central eight-membered ring, which contains an enol-ester, from which five arms extend. The arms exhibit intermolecular interactions within the crystal lattice between molecules of the title compound and with co-crystallized solvent molecules (acetonitrile).
Crystallization‐induced emission (CIE) has been reported for a handful of polyaromatic molecules,... more Crystallization‐induced emission (CIE) has been reported for a handful of polyaromatic molecules, and this phenomenon has been generally ascribed to blocking of nonradiative energy dissipation pathways through crystalline organizations. Herein, the first use of a single‐ring CIE‐based “invisible” ink is reported, which can be applied on varied surfaces. The ink comprises (3E)‐4‐[4‐(methylsulfanyl)phenyl]‐3‐buten‐2‐one (MSPB), exhibiting remarkable spontaneous water and interface‐induced CIE. The molecule, which is synthesized through a facile one‐step process, is nonfluorescent when dissolved in polar organic solvents but forms fluorescent crystalline assemblies upon addition of water or upon drying on solid substrates. X‐ray diffraction analysis reveals that the fluorescent crystalline structure of MSPB is stabilized both by intermolecular C⋅⋅⋅HO and C⋅⋅⋅Hπ interactions among adjacent molecules. The readily adopted crystalline organization of MSPB facilitates its use as a fluorescent ink on diverse substrates, including paper, metals, polymers, and ceramic surfaces. Crystallization‐induced emission (CIE) of a molecule displaying a single phenyl ring is reported. The fluorescence emission is ascribed to the crystalline organization of the molecule, blocking π–π stacking and concomitant nonradiative energy dissipation. The CIE phenomenon is exploited for utilizing the molecule as an “invisible ink” on a variety of surfaces.
Alcohols, with hydroxyl groups compositionally identical to water itself, are consummate hydrophi... more Alcohols, with hydroxyl groups compositionally identical to water itself, are consummate hydrophiles, whose high solubilities preclude spontaneous self-assembly in water. Nevertheless, the solute-solvent interactions associated with their highly favorable solvation enthalpies impose substantial entropic costs, similar in magnitude to those that drive the hydrophobic assembly of alkanes. We now show that under nanoconfined conditions this normally dormant "hydrophobicity" can emerge as the driving force for alcohol encapsulation. Using a porous molecular capsule, the displacement of endohedrally coordinated formate ligands (HCO2-) by 1,2-hydroxyl-functionalized l-glycerate (l-gly, l-HOCH2(HO)CHCO2-) was investigated by van't Hoff analysis of variable-temperature 1H NMR in D2O. At pD 5.8, l-gly uptake is enthalpically inhibited. Upon attenuation of this unfavorable change in enthalpy by cosequestration of protons within the alcoholic environment provided by encapsulated diol-functionalized ligands, - TΔ S° dominates over Δ H°, spontaneously filling the capsule to its host capacity of 24 l-gly ligands via an entropically driven hydrophobic response.
While sophisticated computational methods can predict 31P NMR spectra of phosphorus atoms encapsu... more While sophisticated computational methods can predict 31P NMR spectra of phosphorus atoms encapsulated within Keggin-derived heteropoly tungstate and molybdate cluster anions, calculated and experimental chemical shift values typically deviate considerably from one another. Motivated by the observation that experimentally determined 31P chemical shift values within a series of water-soluble plenary and metal-cation substituted lacunary Keggin anions, [PMnW11O39](7–n)– (Mn = Ag+, Zn2+, Nb5+, W6+) and [(PW11O39)2Mn](14–n)– (Mn = Y3+, Zr4+), varied as a linear function of the oxidation states, n, of the complexed Mn cations, a linear correlation was sought between observed chemical shift values and the net Coulombic forces experienced by the encapsulated phosphorus atoms. The Coulombic model based on Shannon radii, published electronegativity values, and bond angles from X-ray crystallographic data remarkably accounted for the relative 31P chemical shift values of phosphorus atoms in over 50 metal-oxide cluster anions, including large structures comprised of up to four Keggin-derived fragments with an overall R2 value of 0.974. With the model being applied here to three cluster anions whose 31P chemical shift values are reported here for the first time, predicted and experimental values differed by only ±0.4 ppm.
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Papers by Mark Baranov