Title: Seeing luminescence appear as crystals crumble. Isolation and subsequent self-association of individual [(C 6 H 11 NC) 2 Au] + ions in crystals
Non-luminescent, isostructural crystals of [(C 6 H 11 NC) 2 Au](EF 6 )·C 6 H 6 (E = As, Sb) lose benzene upon standing in air to produce green luminescent (E = As) or blue luminescent (E = Sb) powders. Previous studies have shown that the two-coordinate cation, [(C 6 H 11 NC) 2 Au] + , self-associates to form luminescent crystals that contain linear or nearly linear chains of cations and display unusual polymorphic, vapochromic, and/or thermochromic properties. Here, we report the formation of non-luminescent crystalline salts in which individual [(C 6 H 11 NC) 2 Au] + ions are isolated from one another. In [(C 6 H 11 NC) 2 Au](BArF 24 ) ((BArF 24 ) − is tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) each cation is surrounded by two anions that prohibit any close approach of the gold ions. Crystallization of [(C 6 H 11 NC) 2 Au](EF 6 ) (E = As or Sb, but not P) from benzene solution produces colorless, non-emissive crystals of the solvates [(C 6 H 11 NC) 2 Au](EF 6 )·C 6 H 6 . These two solvates are isostructural and contain columns in which cations and benzene molecules alternate. With the benzene molecules separating the cations, the shortest distances between gold ions are 6.936(2) Å for E = As and 6.9717(19) Å for E = Sb. Upon removal from the mother liquor, these crystals crack due to the loss of benzene from the crystal and form luminescent powders. Crystals of [(C 6 H 11 NC) 2 Au](SbF 6 )·C 6 H 6 that powder out form a pale yellow powder with a blue luminescence with emission spectra and powder X-ray diffraction data that show that the previously characterized [(C 6 H 11 NC) 2 Au](SbF 6 ) is formed. In the process, the distances between the gold( i ) ions decrease to ∼3 Å and half of the cyclohexyl groups move from an axial orientation to an equatorial one. Remarkably, when crystals of [(C 6 H 11 NC) 2 Au](AsF 6 )·C 6 H 6 stand in air, they lose benzene and are converted into the yellow, green-luminescent polymorph of [(C 6 H 11 NC) 2 Au](AsF 6 ) rather than the colorless, blue-luminescent polymorph. Paradoxically, the yellow, green-luminescent powder that forms as well as authentic crystals of the yellow, green-luminescent polymorph of [(C 6 H 11 NC) 2 Au](AsF 6 ) are sensitive to benzene vapor and are converted by exposure to benzene vapor into the colorless, blue-luminescent polymorph. more »« less
Luong, Lucy M.; Olmstead, Marilyn M.; Balch, Alan L.
(, Chemical Communications)
null
(Ed.)
The discovery of a third, non-luminescent crystalline polymorph of [(C 6 H 11 NC) 2 Au]PF 6 is reported. Remarkably, crystals of this polymorph are sensitive to mechanical pressure or to exposure to dichloromethane vapor. In both cases, the conversion produces the yellow, green luminescent polymorph of [(C 6 H 11 NC) 2 Au]PF 6 and not the colorless, blue luminescent polymorph.
Costa, Sarah; Walters, Daniel T; McNamara, Lauren E; Olmstead, Marilyn M; Fettinger, James C; Balch, Alan L
(, Inorganic Chemistry)
Six salts ([Au2(μ-dppe)2](BF4)2·CHCl3, [Au2(μ- dppe)2](BF4)2·1,2-Cl2C2H4, [Au2(μ-dppe)2](PF6)2·CHCl3, [Au2(μ-dppe)2](PF6)2, [Au2(μ-dppe)2](SbF6)2, and [Au2(μ- dppe)2](OTf)2·2CHCl3), (dppe is bis(diphenylphosphine)ethane) containing the dication, [Au2(μ-dppe)2]2+, have been prepared and structurally characterized by single-crystal X-ray crystallography. Unlike the three-coordinate dppe-bridged dimers, Au2X2(μ-dppe)2 (X = Br, I), which show considerable variation in the distance between the gold(I) ions over the range 3.0995(10) to 3.8479(3) Å in various solvates, the structure of the helical dication, [Au2(μ- dppe)2], in the new salts is remarkably consistent with the Au···Au separation falling in the narrow range 2.8787(9) to 2.9593(5) Å. In the solid state, the six crystals display a green luminescence both at room temperature and at 77 K, which has been assigned as phosphorescence. However, solutions of the dication are not luminescent. Salts containing the analogous dication [Au2(μ-dppp)2](PF6)2 (dppp is bis(diphenylphosphine)propane) have been prepared to determine whether the longer bridging ligand might also twist into a helical shape. These salts include [Au2(μ- dppp)2](OTf)2 (OTf is triflate) and three crystalline forms of [Au2(μ-dppp)2](PF6)2: the solvate [Au2(μ-dppp)2](PF6)2·(CHCl3) and two polymorphs of the unsolvated salt. None of these crystals are luminescent, but all contain a similar dication, [Au2(μ- dppp)2]2+, that contains two nearly parallel, linear P−Au−P groups and a long separation between the gold ions that varies from 5.3409(4) to 5.6613(6)Å.
Costa, Sarah; Aristov, Michael M; Lim, Sang Ho; Chui, Sarah M; Espinoza, Katelyn A; Olmstead, Marilyn M; Fettinger, James C; Berry, John F; Balch, Alan L
(, Inorganic Chemistry)
We report the ability to trap the dimer Au2(μ-dppe)2I2 (dppe is 1,2- bis(diphenylphosphino)ethane) with different separations between the three-coordinate gold ions in crystalline solvates. All of these solvates ((Au2(μ-dppe)2I2·4(CH2Cl2) (1), Au2(μ- dppe)2I2·2(CH2Cl2) (2), the polymorphs α-Au2(μ-dppe)2I2·2(HC(O)NMe2) (3) and β- Au2(μ-dppe)2I2·2(HC(O)NMe2) (4), and Au2(μ-dppe)2I2·4(CHCl3) (5)) along with polymeric {Au(μ-dppe)I}n·n(CHCl3) (6)) originated from the same reaction, only the solvent system used for crystallization differed. In the different solvates of Au2(μ-dppe)2I2, the Au···Au separation varied from 3.192(1) to 3.7866(3) Å. Computational studies undertaken to understand the flexible nature of these dimers indicated that the structural differences were primarily a result of crystal packing effects with aurophillic interactions having a minimal effect.
Abstract Herein, the first report on the isolated and unambiguously proven benzene radical trianion is presented. This unprecedented radical oxidation state of benzene is stabilized through two trivalent rare earth (RE) metal cations each supported by a bis(guanidinate) scaffold. Specifically, the one‐electron chemical reduction of the neutral inverse‐sandwich yttrium complex [[{(Me3Si)2NC(NiPr)2}2Y]2(μ–ƞ6:ƞ6–C6H6)]1, containing a benzene dianion, with potassium graphite (KC8) in the presence of [2.2.2]‐cryptand yielded the title complex [K([2.2.2]‐cryptand)][[{(Me3Si)2NC(NiPr)2}2Y]2(μ–ƞ6:ƞ6–C6H6•)]2, featuring a benzene radical trianion. Analyses through single‐crystal X‐ray diffraction, EPR and UV–vis spectroscopy, elucidated its molecular structure and revealed strong [YIII–(C6H6)3–•–YIII] metal–radical interactions. Although the Y centers remain in the +3 oxidation state, the spin density of the unpaired electron resides primarily on the benzene trianion moiety and extends toward the YIIIions. Density functional theory (DFT) calculations on2corroborate this assignment and further suggest weak aromaticity for the benzene radical trianion.
Walters, Daniel T; Costa, Sarah; Aghakhanpour, Reza Babadi; Olmstead, Marilyn M; Balch, Alan L
(, Polyhedron)
Two luminescent salts, [Au6(Triphos)4Au(CN)2](CF3SO3)5⋅5CH2Cl2⋅C6H5CH3 (1) and [Au6(Triphos)4] (PF6)6⋅2CH2Cl2⋅6C6H5CH3⋅H2O (2) where Triphos is bis(2-diphenyl-phosphinoethyl)phenylphosphine have been prepared from non-luminescent precursors. The luminescence in each salt results from aurophilic interactions between two or three gold(I) ions. Crystals of [Au6(Triphos)4Au(CN)2](CF3SO3)5⋅5CH2Cl2⋅C6H5CH3 (1) contain a box-like structure with an [Au(CN)2]− ion suspended between two gold(I) ions in the box. Crystals of [Au6(Triphos)4](PF6)6⋅2CH2Cl2⋅6C6H5CH3⋅H2O (2) contain a partial helical structure with pairs of gold(I) ions closely connected and surrounded by helical Ph2PCH2CH2PPh-units from two Triphos ligands.
Luong, Lucy M., Lowe, Christopher D., Adams, Alexandria V., Moshayedi, Venoos, Olmstead, Marilyn M., and Balch, Alan L. Seeing luminescence appear as crystals crumble. Isolation and subsequent self-association of individual [(C 6 H 11 NC) 2 Au] + ions in crystals. Retrieved from https://par.nsf.gov/biblio/10272481. Chemical Science 11.43 Web. doi:10.1039/d0sc03299a.
Luong, Lucy M., Lowe, Christopher D., Adams, Alexandria V., Moshayedi, Venoos, Olmstead, Marilyn M., & Balch, Alan L. Seeing luminescence appear as crystals crumble. Isolation and subsequent self-association of individual [(C 6 H 11 NC) 2 Au] + ions in crystals. Chemical Science, 11 (43). Retrieved from https://par.nsf.gov/biblio/10272481. https://doi.org/10.1039/d0sc03299a
Luong, Lucy M., Lowe, Christopher D., Adams, Alexandria V., Moshayedi, Venoos, Olmstead, Marilyn M., and Balch, Alan L.
"Seeing luminescence appear as crystals crumble. Isolation and subsequent self-association of individual [(C 6 H 11 NC) 2 Au] + ions in crystals". Chemical Science 11 (43). Country unknown/Code not available. https://doi.org/10.1039/d0sc03299a.https://par.nsf.gov/biblio/10272481.
@article{osti_10272481,
place = {Country unknown/Code not available},
title = {Seeing luminescence appear as crystals crumble. Isolation and subsequent self-association of individual [(C 6 H 11 NC) 2 Au] + ions in crystals},
url = {https://par.nsf.gov/biblio/10272481},
DOI = {10.1039/d0sc03299a},
abstractNote = {Non-luminescent, isostructural crystals of [(C 6 H 11 NC) 2 Au](EF 6 )·C 6 H 6 (E = As, Sb) lose benzene upon standing in air to produce green luminescent (E = As) or blue luminescent (E = Sb) powders. Previous studies have shown that the two-coordinate cation, [(C 6 H 11 NC) 2 Au] + , self-associates to form luminescent crystals that contain linear or nearly linear chains of cations and display unusual polymorphic, vapochromic, and/or thermochromic properties. Here, we report the formation of non-luminescent crystalline salts in which individual [(C 6 H 11 NC) 2 Au] + ions are isolated from one another. In [(C 6 H 11 NC) 2 Au](BArF 24 ) ((BArF 24 ) − is tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) each cation is surrounded by two anions that prohibit any close approach of the gold ions. Crystallization of [(C 6 H 11 NC) 2 Au](EF 6 ) (E = As or Sb, but not P) from benzene solution produces colorless, non-emissive crystals of the solvates [(C 6 H 11 NC) 2 Au](EF 6 )·C 6 H 6 . These two solvates are isostructural and contain columns in which cations and benzene molecules alternate. With the benzene molecules separating the cations, the shortest distances between gold ions are 6.936(2) Å for E = As and 6.9717(19) Å for E = Sb. Upon removal from the mother liquor, these crystals crack due to the loss of benzene from the crystal and form luminescent powders. Crystals of [(C 6 H 11 NC) 2 Au](SbF 6 )·C 6 H 6 that powder out form a pale yellow powder with a blue luminescence with emission spectra and powder X-ray diffraction data that show that the previously characterized [(C 6 H 11 NC) 2 Au](SbF 6 ) is formed. In the process, the distances between the gold( i ) ions decrease to ∼3 Å and half of the cyclohexyl groups move from an axial orientation to an equatorial one. Remarkably, when crystals of [(C 6 H 11 NC) 2 Au](AsF 6 )·C 6 H 6 stand in air, they lose benzene and are converted into the yellow, green-luminescent polymorph of [(C 6 H 11 NC) 2 Au](AsF 6 ) rather than the colorless, blue-luminescent polymorph. Paradoxically, the yellow, green-luminescent powder that forms as well as authentic crystals of the yellow, green-luminescent polymorph of [(C 6 H 11 NC) 2 Au](AsF 6 ) are sensitive to benzene vapor and are converted by exposure to benzene vapor into the colorless, blue-luminescent polymorph.},
journal = {Chemical Science},
volume = {11},
number = {43},
author = {Luong, Lucy M. and Lowe, Christopher D. and Adams, Alexandria V. and Moshayedi, Venoos and Olmstead, Marilyn M. and Balch, Alan L.},
editor = {null}
}
Warning: Leaving National Science Foundation Website
You are now leaving the National Science Foundation website to go to a non-government website.
Website:
NSF takes no responsibility for and exercises no control over the views expressed or the accuracy of
the information contained on this site. Also be aware that NSF's privacy policy does not apply to this site.
An official website of the United States government
