The photodissociation dynamics of alkyl iodides along the C–I bond are captured by attosecond extreme-ultraviolet (XUV) transient absorption spectroscopy employing resonant ∼20 fs UV pump pulses. The methodology of previous experiments on CH3I [Chang et al., J. Chem. Phys. 154, 234301 (2021)] is extended to the investigation of a C–I bond-breaking reaction in the dissociative A-band of C2H5I, i-C3H7I, and t-C4H9I. Probing iodine 4 d core-to-valence transitions in the XUV enables one to map wave packet bifurcation at a conical intersection in the A-band as well as coherent vibrations in the ground state of the parent molecules. Analysis of spectroscopic bifurcation signatures yields conical intersection crossing times of 15 ± 4 fs for CH3I, 14 ± 5 fs for C2H5I, and 24 ± 4 fs for i-C3H7I and t-C4H9I, respectively. Observations of coherent vibrations, resulting from a projection of A-band structural dynamics onto the ground state by resonant impulsive stimulated Raman scattering, indirectly reveal multimode C–I stretch and CCI bend vibrations in the A-bands of C2H5I, i-C3H7I, and t-C4H9I.
Conical intersections between electronic states often dictate the chemistry of photoexcited molecules. Recently developed sources of ultrashort extreme ultraviolet (XUV) pulses tuned to element-specific transitions in molecules allow for the unambiguous detection of electronic state-switching at a conical intersection. Here, the fragmentation of photoexcited
- Award ID(s):
- 1660417
- NSF-PAR ID:
- 10183255
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Nature Communications
- Volume:
- 11
- Issue:
- 1
- ISSN:
- 2041-1723
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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By varying the halogen-bond-donor molecule, 11 new halogen-bonding cocrystals involving thiourea or 1,3-dimethylthiourea were obtained, namely, 1,3-dimethylthiourea–1,2-diiodo-3,4,5,6-tetrafluorobenzene (1/1), C 6 F 4 I 2 ·C 3 H 8 N 2 S, 1 , thiourea–1,3-diiodo-2,4,5,6-tetrafluorobenzene (1/1), C 6 F 4 I 2 ·CH 4 N 2 S, 2 , 1,3-dimethylthiourea–1,3-diiodo-2,4,5,6-tetrafluorobenzene (1/1), C 6 F 4 I 2 ·C 3 H 8 N 2 S, 3 , 1,3-dimethylthiourea–1,3-diiodo-2,4,5,6-tetrafluorobenzene–methanol (1/1/1), C 6 F 4 I 2 ·C 3 H 8 N 2 S·CH 4 O, 4 , 1,3-dimethylthiourea–1,3-diiodo-2,4,5,6-tetrafluorobenzene–ethanol (1/1/1), C 6 F 4 I 2 ·C 3 H 8 N 2 S·C 2 H 6 O, 5 , 1,3-dimethylthiourea–1,4-diiodo-2,3,5,6-tetrafluorobenzene (1/1), C 6 F 4 I 2 ·C 3 H 8 N 2 S, 6 , 1,3-dimethylthiourea–1,3,5-trifluoro-2,4,6-triiodobenzene (1/1), C 6 F 3 I 3 ·C 3 H 8 N 2 S, 7 , 1,3-dimethylthiourea–1,1,2,2-tetraiodoethene (1/1), C 6 H 16 N 4 S 2 ·C 2 I 4 , 8 , [(dimethylamino)methylidene](1,2,2-triiodoethenyl)sulfonium iodide–1,1,2,2-tetraiodoethene–acetone (1/1/1), C 5 H 8 I 3 N 2 S + ·I − ·C 3 H 6 O·C 2 I 4 , 9 , 2-amino-4-methyl-1,3-thiazol-3-ium iodide–1,1,2,2-tetraiodoethene (2/3), 2C 4 H 7 N 2 S + ·2I − ·3C 2 I 4 , 10 , and 4,4-dimethyl-4 H -1,3,5-thiadiazine-3,5-diium diiodide–1,1,2,2-tetraiodoethene (2/3), 2C 5 H 12 N 4 S 2+ ·4I − ·3C 2 I 4 , 11 . When utilizing the common halogen-bond-donor molecules 1,2-, 1,3-, and 1,4-diiodotetrafluorobenzene, as well as 1,3,5-trifluoro-2,4,6-triiodobenzene, bifurcated I...S...I interactions were observed, resulting in the formation of isolated rings, chains, and sheets. Tetraiodoethylene (TIE) provided I...S...I cocrystals as well, but further yielded a sulfonium-containing product through the reaction of the S atom with TIE. This particular sulfonium motif is the first of its kind to be structurally characterized, and is stabilized in the solid state through a three-dimensional I...I halogen-bonding network. Thiourea reacted with acetone in the presence of TIE to provide two novel heterocyclic products, again stabilized in the solid state through I...I halogen bonding.more » « less
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Abstract Photoexcited organic chromophores appended to stable radicals can serve as qubit and/or qudit candidates for quantum information applications. 1,6,7,12‐Tetra‐(4‐
tert ‐butylphenoxy)‐perylene‐3,4 : 9,10‐bis(dicarboximide) (tpPDI) linked to a partially deuterated α,γ‐bisdiphenylene‐β‐phenylallyl radical (BDPA‐d 16) was synthesized and characterized by time‐resolved optical and electron paramagnetic resonance (EPR) spectroscopies. Photoexcitation of tpPDI‐BDPA‐d 16results in ultrafast radical‐enhanced intersystem crossing to produce a quartet state (Q ) followed by formation of a spin‐polarized doublet ground state (D 0). Pulse‐EPR experiments confirmed the spin multiplicity ofQ and yielded coherence times ofT m=2.1±0.1 μs and 2.8±0.2 μs forQ andD 0, respectively. BDPA‐d 16eliminates the dominant1H hyperfine couplings, resulting in a single narrow line for both theQ andD 0states, which enhances the spectral resolution needed for good qubit addressability.
