Laura McCaslin

One of the most inspiring talks I've ever seen!

Our group is currently looking for a #compchem #postdoc to start in Fall 2025. Primary area of research will be with the NSF Center for the Mechanical Control of Chemistry (CMCC), with second focus in organic materials/molecular design. More info at: dtaborgroup.com/openings/ Apply by Aug 10.

I'm so happy to hear this!! Sending my warmest congratulations and luck to you and your group!

Quantifying Design Principles for Light-Emitting Materials with Inverted Singlet–Triplet Energy Gaps Molecular engineering of organic emitter molecules with inverted singlet–triplet energy gaps (INVEST) has emerged as a powerful approach for enhancing fluorescence efficiency through triplet harvesting. In these unique materials, the first excited singlet state (S1) lies below the lowest triplet state (T1), enabling efficient reverse intersystem crossing. Previous computational studies have focused on accurately calculating the inverted energy gap and establishing qualitative structure–property relationships. Here, we present quantitative relationships that link the molecular structure to the S1–T1 energy gap, ΔEST, by introducing a benchmark set of 15 heptazine-based INVEST molecules (HEPTA-INVEST15). We identify a strong linear correlation (R2 > 0.94) between ΔEST and both the degree of intramolecular charge transfer and the deviation from a single-excitation character, as quantified by %R1 values and transition density matrix norms. These trends persist across our expanded set of 44 mono-, di-, and tri-substituted heptazines (HEPTA-INVEST44), underscoring the generality of our findings. Notably, strongly electron-donating groups, such as −NH2, minimize the magnitude of inverted gaps in mono-substituted heptazines yet produce the most negative ΔEST in certain tri-substituted derivatives, a result arising from competing resonance effects and excited-state aromaticity. Although ΔEST shows no clear correlation with Hammett parameters, our results reveal that physically meaningful, computable descriptors offer a mechanistic foundation for the future data-driven design of INVEST emitters. These findings pave the way for machine-learning approaches that connect the molecular structure to ΔEST without requiring high-level excited-state calculations.

Check out our recent paper where we quantify structure-property relationships in organic emitters for enhanced fluorescence! 🧪 pubs.acs.org/doi/full/10.... #chemsky #compchem

Excited to announce that I will be hosting Sam Biggerstaff, PhD candidate at UGA, as a SCGSR intern this year! We will be developing new theoretical tools for observing geometric phase effects in molecular reactions. www.energy.gov/science/arti...

This is so cool! Congrats, Nate!

Quantifying design principles for light-emitting materials with inverted singlet-triplet energy gaps Molecular engineering of organic emitter molecules with inverted singlet-triplet energy gaps (INVEST) has emerged as a powerful approach to achieve enhanced fluorescence efficiency through triplet har...

Check out our new pre-print on quantitative structure-property relationships for organic emitters with inverted singlet-triplet states (INVEST)! #ChemSky 🧪
chemrxiv.org/engage/chemr...

Laura M. McCaslin Biography Laura M. McCaslin is a Senior Member of the Technical Staff in the CRF at Sandia.  Her research program centers on computing the dynamics of molecular systems and materials.  Her research pr...

Hello, will you please add me to the list? crf.sandia.gov/staff/laura-...

We believe this novel technology has the potential for major impacts in the rapidly growing fields of quantum information, specifically single-molecule quantum sensing!

The unique design of this revolutionary experiment enables the detection of coherence transfer between vibrational states, which has long been a holy grail for understanding fundamental quantum mechanical energy transfer between vibrational states in molecules.

Coherent Vibrational Dynamics in an Isolated Peptide Captured with Two-Dimensional Infrared Spectroscopy Quantum mechanical vibrational coherence transfer processes play important roles in energy relaxation, charge transfer, and reaction dynamics in chemical and biological systems but are difficult to directly measure using traditional condensed-phase nonlinear spectroscopies. Recently, we developed a new experimental capability to obtain two-dimensional infrared (2D IR) spectra of molecular systems in the gas phase that enables the direct measurement of coherence pathways. Herein, we report ultrafast 2D IR spectroscopy of the peptide glutathione (GSH) isolated and cryogenically cooled in the gas phase. Six vibrational modes were simultaneously excited within the amide I and II region. The spectral dynamics of both diagonal and off-diagonal cross peak features exhibit long-lived oscillatory behavior consistent with the presence of coherent vibrational dynamics. The oscillatory signatures deviate significantly from the expected quantum beating pathways predicted from standard nonlinear response theories. These deviations indicate the presence of additional nonlinear pathways, including coherence transfer processes. Quantum chemistry calculations indicate large anharmonic couplings between the excited vibrational modes in GSH and, critically, strong coupling between the excited modes and numerous low-frequency modes that act as a bath to mediate coherence transfer. The data provide important new benchmarks for modeling coherence transfer dynamics and system–bath interactions in open quantum systems free from solvent effects.

Thrilled to see our paper the gas-phase 2D IR spectroscopy of a tripeptide published in JACS! Prof. Joe Fournier and Zifan Ma at WashU developed a first-in-the-world experiment which reveals the ubiquity of coherent vibrational dynamics in molecules. pubs.acs.org/doi/abs/10.1... #ChemSky 🧪

We are excited to announce a new paper, “Environmental Photosensitizers Can Exhibit Enhanced Actinic Absorption in Microhydrated Clusters Compared to Solution”. Check it out! doi.org/10.1016/j.Ji... #ChemSky 🧪

#chemsky

Coherent Vibrational Dynamics in an Isolated Peptide Captured with 2D IR Spectroscopy Quantum mechanical vibrational coherence transfer processes play important roles in energy relaxation, charge transfer, and reaction dynamics in chemical and biological systems, but are difficult to d...

A beautiful new experiment from Joe Fournier’s lab at Wash U enables 2D IR in the gas phase! The action spectroscopy method enables clear detection of coherence transfer, which is extremely challenging to resolve in condensed phase. Thrilled to be a part of this work: chemrxiv.org/engage/chemr...

Check out our paper on the electronic structure of excited states involved in ~200 nm photodissociation of dimethyl disulfide, a key model system to understand how proteins and peptides break down in sunlight! #chemsky

pubs.rsc.org/en/content/a...

There you have it! After 12 years as a theorist, I’m back to being an experimentalist (for the weekend).

It’s been a great beam time at SLAC’s MeV UED facility so far. Can’t wait to start analyzing our results! 🧪#ChemSky #SciSky

Postdoctoral Appointee in Computational Quantum Chemistry (Onsite)Radius Icon

sandia.jobs/livermore-ca...

Hi all! I have a postdoc position open for a project studying the effects of shaped femtosecond laser pulses on molecular dynamics. We'll use electronic structure theory, quantum dynamics methods, and optimal control theory to predict ultrafast spectroscopy. #chemsky

Some thoughts for the academic recommendation letter season; a poem from the December 2023 issue of Poetry Magazine, by Keith Leonard. #poetry

Just out in JPC Lett!

High-throughout screening of molecular materials’ optical properties is difficult! We developed a new chemical rule to determine an optical property of donor-acceptor materials using ground state orbital analysis alone. 🧪 #ChemSky

pubs.acs.org/doi/epdf/10....

Thanks for putting this together! www.sandia.gov/crf/staff/la...

Our paper investigating the structure and properties of new materials for next-generation optoelectronic devices has been selected as a 2023 HOT article in Physical Chemistry Chemical Physics!

pubs.rsc.org/en/content/a...

Comparing the structures and photophysical properties of two charge transfer co-crystals Organic co-crystals have emerged as a promising class of semiconductors for next-generation optoelectronic devices due to their unique photophysical properties. This paper presents a joint experimenta...

Here’s the latest paper from the team! We compare the crystal structures, spectroscopy, and electronic structure of two charge transfer co-crystals to identify candidate materials for next-generation optoelectronic devices.

doi.org/10.1039/D3CP...

A photo of the incredible team of postdocs I get to work with at Sandia! It was a rare event to catch us all in one place at the Fall American Chemical Society meeting in San Francisco!