∆DFT predicts inverted singlet-triplet gaps with chemical accuracy at a fraction of the cost of wavefunction-based approaches

Published: June 3, 2024

Efficient OLEDs must quickly convert singlet and triplet excitons into photons. Molecules with an inverted singlet-triplet energy gap (INVEST) are promising candidates for this task. However, typical INVEST molecules have drawbacks like too low oscillator strengths excitation energies. High-throughput screening could identify suitable molecules, but existing methods problematic: The workhorse method TD-DFT cannot reproduce inversion, while wavefunction-based slow. This study proposes a state-specific based on unrestricted Kohn-Sham DFT common hybrid functionals. Tuned the new INVEST15 benchmark set, achieves error of less than 1 kcal/mol, which is traced back to cancellation between spin contamination dynamic correlation. Applied larger structurally diverse NAH159 set in black-box fashion, maintains small (1.2 kcal/mol) accurately predicts signs 83% cases, confirming its robustness suitability workflows.

Language: Английский

Femtosecond core-level spectroscopy reveals involvement of triplet states in the gas-phase photodissociation of Fe(CO)5

Published: June 3, 2024

Excitation of iron pentacarbonyl [Fe(CO)5], a prototypical photocatalyst, at 266 nm causes sequential loss two CO ligands in the gas phase, creating catalytically active, unsaturated carbonyls. Despite numerous studies, major aspects its ultrafast photochemistry remain unresolved because early excited-state dynamics have so far eluded spectroscopic observation. This has led to long-held assumption that dissociation gas-phase Fe(CO)5 proceeds exclusively on singlet manifold. Herein, we present combined experimental-theoretical study employing extreme ultraviolet transient absorption spectroscopy near Fe M2 ,3-edge, which features spectral evolution 100-fs and 3-ps time scales, alongside high-level electronic structure theory, enables characterization molecular geometries states involved photodissociation Fe(CO)5. We assign signatures associated with intertwined structural metal-centered during first loss, competing Fe(CO)4 along lowest triplet surfaces form Fe(CO)3. Calculations spectra both as well spin-orbit coupling constants key pathways, provide evidence for intersystem crossing ground state Fe(CO)4. Thus, our work presents detection excited challenges long-standing do not play role dynamics.

Language: Английский

Femtosecond core-level spectroscopy reveals involvement of triplet states in the gas-phase photodissociation of Fe(CO)5

Published: June 5, 2024

Excitation of iron pentacarbonyl [Fe(CO)5], a prototypical photocatalyst, at 266 nm causes sequential loss two CO ligands in the gas phase, creating catalytically active, unsaturated carbonyls. Despite numerous studies, major aspects its ultrafast photochemistry remain unresolved because early excited-state dynamics have so far eluded spectroscopic observation. This has led to long-held assumption that dissociation gas-phase Fe(CO)5 proceeds exclusively on singlet manifold. Herein, we present combined experimental-theoretical study employing extreme ultraviolet transient absorption spectroscopy near Fe M2 ,3-edge, which features spectral evolution 100-fs and 3-ps time scales, alongside high-level electronic structure theory, enables characterization molecular geometries states involved photodissociation Fe(CO)5. We assign signatures associated with intertwined structural metal-centered during first loss, competing Fe(CO)4 along lowest triplet surfaces form Fe(CO)3. Calculations spectra both as well spin-orbit coupling constants key pathways, provide evidence for intersystem crossing ground state Fe(CO)4. Thus, our work presents detection excited challenges long-standing do not play role dynamics.

Language: Английский