14 research outputs found
Effects of the reaction cavity on metastable optical excitation in ruthenium-sulfur dioxide complexes
We report photoexcited-state crystal structures for two new members of the
[Ru(SO_2)(NH_3)_4X]Y family: 1:X=H2O, Y=(+/-)-camphorsulfonate_2;
2:X=isonicotinamide, Y=tosylate_2. The excited states are metastable at 100 K,
with a photoconversion fraction of 11.1(7)% achieved in 1, and 22.1(10)% and
26.9(10)% at the two distinct sites in 2.We further show using solid-state
density-functional-theory calculations that the excited-state geometries
achieved are strongly influenced by the local crystal environment. This result
is relevant to attempts to rationally design related photoexcitation systems
for optical data-storage applications.Comment: 6 pages, 5 figure
Discovery of Black Dye Crystal Structure Polymorphs: Implications for Dye Conformational Variation in Dye-Sensitized Solar Cells
We present the discovery of a new
crystal structure polymorph (<b>1</b>) and pseudopolymorph (<b>2</b>) of the Black Dye, one of the world’s leading dyes
for dye-sensitized solar cells, DSSCs (10.4% device performance efficiency).
This reveals that Black Dye molecules can adopt multiple low-energy
conformers. This is significant since it challenges existing models
of the Black Dye···TiO<sub>2</sub> adsorption process
that renders a DSSC working electrode; these have assumed a single
molecular conformation that refers to the previously reported Black
Dye crystal structure (<b>3</b>). The marked structural differences
observed between <b>1</b>, <b>2</b>, and <b>3</b> make the need for modeling multiple conformations more acute. Additionally,
the ordered form of the Black Dye (<b>1</b>) provides a more
appropriate depiction of its anionic structure, especially regarding
its anchoring group and NCS bonding descriptions. The tendency toward
NCS ligand isomerism, evidenced via the disordered form <b>2</b>, has consequences for electron injection and electron recombination
in Black Dye embedded DSSC devices. Dyes <b>2</b> and <b>3</b> differ primarily by the absence or presence of a solvent
of crystallization, respectively; solvent environment effects on the
dye are thereby elucidated. This discovery of multiple Black Dye conformers
from diffraction, with atomic-level definition, complements recently
reported nanoscopic evidence for multiple dye conformations existing
at a dye···TiO<sub>2</sub> interface, for a chemically
similar DSSC dye; those results emanated from imaging and spectroscopy,
but were unresolved at the submolecular level. Taken together, these
findings lead to the general notion that multiple dye conformations
should be explicitly considered when modeling dye···TiO<sub>2</sub> interfaces in DSSCs, at least for ruthenium-based dye complexes
Solvent Effects on the UV–vis Absorption and Emission of Optoelectronic Coumarins: a Comparison of Three Empirical Solvatochromic Models
Coumarins often function in the solution
phase for a diverse range
of optoelectronic applications. The associated solvent effects on
the UV–vis absorption and/or fluorescence spectral shifts of
coumarins need to be understood in order that their photochemistry
can be controlled. To this end, three different empirical solvatochromic
models are assessed against 13 coumarins. The two generalized solvent
scales developed by Catalán and co-workers demonstrate comparable
performance to the popular Taft–Kamlet solvatochromic comparison
method. A combinatorial approach to determine the best-fit equations
in all of the empirical models is applied; this involves both statistical
best-fits and the physical validation of the resulting parameters,
based on the molecular structures of solvents and solutes and their
corresponding interactions. The findings of this approach are used
to extract useful information about different aspects of solvent effects
on the solvatochromism of coumarins
Discovery of Black Dye Crystal Structure Polymorphs: Implications for Dye Conformational Variation in Dye-Sensitized Solar Cells
We present the discovery of a new
crystal structure polymorph (<b>1</b>) and pseudopolymorph (<b>2</b>) of the Black Dye, one of the world’s leading dyes
for dye-sensitized solar cells, DSSCs (10.4% device performance efficiency).
This reveals that Black Dye molecules can adopt multiple low-energy
conformers. This is significant since it challenges existing models
of the Black Dye···TiO<sub>2</sub> adsorption process
that renders a DSSC working electrode; these have assumed a single
molecular conformation that refers to the previously reported Black
Dye crystal structure (<b>3</b>). The marked structural differences
observed between <b>1</b>, <b>2</b>, and <b>3</b> make the need for modeling multiple conformations more acute. Additionally,
the ordered form of the Black Dye (<b>1</b>) provides a more
appropriate depiction of its anionic structure, especially regarding
its anchoring group and NCS bonding descriptions. The tendency toward
NCS ligand isomerism, evidenced via the disordered form <b>2</b>, has consequences for electron injection and electron recombination
in Black Dye embedded DSSC devices. Dyes <b>2</b> and <b>3</b> differ primarily by the absence or presence of a solvent
of crystallization, respectively; solvent environment effects on the
dye are thereby elucidated. This discovery of multiple Black Dye conformers
from diffraction, with atomic-level definition, complements recently
reported nanoscopic evidence for multiple dye conformations existing
at a dye···TiO<sub>2</sub> interface, for a chemically
similar DSSC dye; those results emanated from imaging and spectroscopy,
but were unresolved at the submolecular level. Taken together, these
findings lead to the general notion that multiple dye conformations
should be explicitly considered when modeling dye···TiO<sub>2</sub> interfaces in DSSCs, at least for ruthenium-based dye complexes
Ru–OSO Coordination Photogenerated at 100 K in Tetraammineaqua(sulfur dioxide)ruthenium(II) (±)-Camphorsulfonate
The photoinduced O-bound coordination mode in RuSO<sub>2</sub> complexes,
previously observed only at 13 K, has been generated at 100 K in tetraammineaqua(sulfur
dioxide)ruthenium(II) (±)-camphorsulfonate. This coordination
state, often denoted MS1, decays to the η<sup>2</sup>-bound
MS2 state, with an estimated half-life of 3.4(8) h and a long-lived
population of 2.9(4)% at 120 K
Ru–OSO Coordination Photogenerated at 100 K in Tetraammineaqua(sulfur dioxide)ruthenium(II) (±)-Camphorsulfonate
The photoinduced O-bound coordination mode in RuSO<sub>2</sub> complexes,
previously observed only at 13 K, has been generated at 100 K in tetraammineaqua(sulfur
dioxide)ruthenium(II) (±)-camphorsulfonate. This coordination
state, often denoted MS1, decays to the η<sup>2</sup>-bound
MS2 state, with an estimated half-life of 3.4(8) h and a long-lived
population of 2.9(4)% at 120 K
Data mining with molecular design rules identifies new class of dyes for dye-sensitised solar cells
A major deficit in suitable dyes is stifling progress in the dye-sensitised solar cell (DSC) industry. Materials discovery strategies have afforded numerous new dyes; yet, corresponding solution-based DSC device performance has little improved upon 11% efficiency, achieved using the N719 dye over two decades ago. Research on these dyes has nevertheless revealed relationships between the molecular structure of dyes and their associated DSC efficiency. Here, such structure-property relationships have been codified in the form of molecular dye design rules, which have been judiciously sequenced in an algorithm to enable large-scale data mining of dye structures with optimal DSC performance. This affords, for the first time, a DSC-specific dye-discovery strategy that predicts new classes of dyes from surveying a representative set of chemical space. A lead material from these predictions is experimentally validated, showing DSC efficiency that is comparable to many well-known organic dyes. This demonstrates the power of this approach
CCDC 997759: Experimental Crystal Structure Determination
Related Article: Jacqueline M. Cole, Kian Sing Low, Hiroaki Ozoe, Panagiota Stathi, Chitoshi Kitamura, Hiroyuki Kurata, Petra Rudolf, Takeshi Kawase|2014|Phys.Chem.Chem.Phys.(PCCP)|16|26684|doi:10.1039/C4CP02645D,An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Material Profiling for Photocrystallography: Relating Single-Crystal Photophysical and Structural Properties of Luminescent Bis-Cyclometalated Iridium-Based Complexes
The
photophysical properties of seven luminescent iridium complexes
are characterized in their single-crystal form, and the photoactivity
is related to their molecular structures. Specifically, solid-state
optical emission spectra and associated lifetimes are determined from
single crystals of iridium complexes containing three bidentate ligands:
two variously substituted 2-phenylbenzothiazoles and either a 2,4-pentadione
(acetylacetone) or 2-pyridinecarboxylic (picolinic) acid. All complexes
studied exhibit emissive behavior in the solid-state which originates
from <sup>3</sup>π–π* and metal-to-ligand-charge-transfer
(MLCT) electronic transitions; this is supported by density functional
theory. Phosphorescence is observed in all cases with microsecond
lifetimes, ranging from 0.30 to 2.4 μs at 298 K and 1.4–4.0
μs at 100 K. Structure–property relationships are established
which are relevant to the potential solid-state application of this
series of luminescent complexes as organic light emitting diodes (OLED)
material components. In addition, these materials are assessed for
their suitability to time-resolved pump–probe photocrystallography
experiments, which will reveal their photoexcited state structure.
Accordingly, the design process by which materials are selected and
technical parameters are defined for a photocrystallography experiment
is illustrated. This family of complexes presents a case study for
this photocrystallography material profiling. Results show that the
time-resolved photoexcited state structure, featuring the MLCT transition
is, in principle at least, viable for two of these complexes
Material Profiling for Photocrystallography: Relating Single-Crystal Photophysical and Structural Properties of Luminescent Bis-Cyclometalated Iridium-Based Complexes
The
photophysical properties of seven luminescent iridium complexes
are characterized in their single-crystal form, and the photoactivity
is related to their molecular structures. Specifically, solid-state
optical emission spectra and associated lifetimes are determined from
single crystals of iridium complexes containing three bidentate ligands:
two variously substituted 2-phenylbenzothiazoles and either a 2,4-pentadione
(acetylacetone) or 2-pyridinecarboxylic (picolinic) acid. All complexes
studied exhibit emissive behavior in the solid-state which originates
from <sup>3</sup>π–π* and metal-to-ligand-charge-transfer
(MLCT) electronic transitions; this is supported by density functional
theory. Phosphorescence is observed in all cases with microsecond
lifetimes, ranging from 0.30 to 2.4 μs at 298 K and 1.4–4.0
μs at 100 K. Structure–property relationships are established
which are relevant to the potential solid-state application of this
series of luminescent complexes as organic light emitting diodes (OLED)
material components. In addition, these materials are assessed for
their suitability to time-resolved pump–probe photocrystallography
experiments, which will reveal their photoexcited state structure.
Accordingly, the design process by which materials are selected and
technical parameters are defined for a photocrystallography experiment
is illustrated. This family of complexes presents a case study for
this photocrystallography material profiling. Results show that the
time-resolved photoexcited state structure, featuring the MLCT transition
is, in principle at least, viable for two of these complexes