Publications by authors named "F N Castellano"

270 Publications

Low power threshold photochemical upconversion using a zirconium(iv) LMCT photosensitizer.

Chem Sci 2021 Jul 2;12(26):9069-9077. Epub 2021 Jun 2.

Department of Chemistry, North Carolina State University Raleigh North Carolina 27695-8204 USA

The current investigation demonstrates highly efficient photochemical upconversion (UC) where a long-lived Zr(iv) ligand-to-metal charge transfer (LMCT) complex serves as a triplet photosensitizer in concert with well-established 9,10-diphenylanthracene (DPA) along with newly conceived DPA-carbazole based acceptors/annihilators in THF solutions. The initial dynamic triplet-triplet energy transfer (TTET) processes (Δ ∼ -0.19 eV) featured very large Stern-Volmer quenching constants ( ) approaching or achieving 10 M with bimolecular rate constants between 2 and 3 × 10 M s as ascertained using static and transient spectroscopic techniques. Both the TTET and subsequent triplet-triplet annihilation (TTA) processes were verified and throughly investigated using transient absorption spectroscopy. The Stern-Volmer metrics support 95% quenching of the Zr(iv) photosensitizer using modest concentrations (0.25 mM) of the various acceptor/annihilators, where no aggregation took place between any of the chromophores in THF. Each of the upconverting formulations operated with continuous-wave linear incident power dependence ( = 514.5 nm) down to ultralow excitation power densities under optimized experimental conditions. Impressive record-setting values ranging from 31.7% to 42.7% were achieved under excitation conditions (13 mW cm) below that of solar flux integrated across the Zr(iv) photosensitizer's absorption band (26.7 mW cm). This study illustrates the importance of supporting the continued development and discovery of molecular-based triplet photosensitizers based on earth-abundant metals.
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http://dx.doi.org/10.1039/d1sc01662hDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8261719PMC
July 2021

Ultrafast Excited-State Dynamics of Photoluminescent Pt(II) Dimers Probed by a Coherent Vibrational Wavepacket.

J Phys Chem Lett 2021 Jul 16:6794-6803. Epub 2021 Jul 16.

Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States.

Intricate potential energy surfaces (PESs) of some transition metal complexes (TMCs) pose challenges in mapping out initial excited-state pathways that could influence photochemical outcomes. Ultrafast intersystem crossing (ISC) dynamics of four structurally related platinum(II) dimer complexes were examined by detecting their coherent vibrational wavepacket (CVWP) motions of Pt-Pt stretching mode in the metal-metal-to-ligand-charge-transfer excited states. Structurally dependent CVWP behaviors (frequency, dephasing time, and oscillation amplitudes) were captured by femtosecond transient absorption spectroscopy, analyzed by short-time Fourier transformation, and rationalized by quantum mechanical calculations, revealing dual ISC pathways. The results suggest that the ligands could fine-tune the PESs to influence the proximity of the conical intersections of the excited states with the Franck-Condon state and thus to control the branching ratio of the dual ISC pathways. This comparative study presents future opportunities in control excited-state trajectories of TMCs via ligand structures.
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http://dx.doi.org/10.1021/acs.jpclett.1c01289DOI Listing
July 2021

Coronavirus Disease 2019 in Children.

Front Pediatr 2021 28;9:668484. Epub 2021 May 28.

Section of Pediatrics, Pediatric Pulmonology Unit, Department of Translational Medical Sciences, Università di Napoli Federico II, Naples, Italy.

Since its appearance in Wuhan in mid-December 2019, acute respiratory syndrome coronavirus 2 (SARS-CoV-2) related 19 coronavirus disease (COVID-19) has spread dramatically worldwide. It soon became apparent that the incidence of pediatric COVID-19 was much lower than the adult form. Morbidity in children is characterized by a variable clinical presentation and course. Symptoms are similar to those of other acute respiratory viral infections, the upper airways being more affected than the lower airways. Thus far, over 90% of children who tested positive for the virus presented mild or moderate symptoms and signs. Most children were asymptomatic, and only a few cases were severe, unlike in the adult population. Deaths have been rare and occurred mainly in children with underlying morbidity. Factors as reduced angiotensin-converting enzyme receptor expression, increased activation of the interferon-related innate immune response, and trained immunity have been implicated in the relative resistance to COVID-19 in children, however the underlying pathogenesis and mechanism of action remain to be established. While at the pandemic outbreak, mild respiratory manifestations were the most frequently described symptoms in children, subsequent reports suggested that the clinical course of COVID-19 is more complex than initially thought. Thanks to the experience acquired in adults, the diagnosis of pediatric SARS-CoV-2 infection has improved with time. Data on the treatment of children are sparse, however, several antiviral trials are ongoing. The purpose of this narrative review is to summarize current understanding of pediatric SARS-CoV-2 infection and provide more accurate information for healthcare workers and improve the care of patients.
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http://dx.doi.org/10.3389/fped.2021.668484DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8193095PMC
May 2021

Next Generation Cuprous Phenanthroline MLCT Photosensitizer Featuring Cyclohexyl Substituents.

Inorg Chem 2021 Jun 7;60(12):8394-8403. Epub 2021 Jun 7.

Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States.

A new long-lived, visible-light-absorbing homoleptic Cu(I) metal-to-ligand charge transfer (MLCT) photosensitizer, [Cu(dchtmp)]PF (dchtmp = 2,9-dicyclohexyl-3,4,7,8-tetramethyl-1,10-phenanthroline), has been synthesized, structurally characterized, and evaluated in terms of its molecular photophysics, electrochemistry, and electronic structure. Static and time-resolved transient absorption (TA) and photoluminescence (PL) spectroscopy measured on the title compound in CHCl (τ = 2.6 μs, Φ = 5.5%), CHCN (τ = 1.5 μs, Φ = 2.6%), and THF (τ = 2.0 μs, Φ = 3.7%) yielded impressive photophysical metrics even when dissolved in Lewis basic solvents. The combined static spectroscopic data along with ultrafast TA experiments revealed that the pseudo-Jahn-Teller distortion and intersystem crossing dynamics in the MLCT excited state displayed characteristics of being sterically arrested throughout its evolution. Electrochemical and static PL data illustrate that [Cu(dchtmp)]PF is a potent photoreductant (-1.77 V vs Fc in CHCN) equal to or greater than all previously investigated homoleptic Cu(I) diimine complexes. Although we successfully prepared the cyclopentyl analog dcptmp (2,9-dicyclopentyl-3,4,7,8-tetramethyl-1,10-phenanthroline) using the same C-C radical coupling photochemistry as dchtmp, the corresponding Cu(I) complex could not be isolated due to the steric hindrance presented at the metal center. Ultimately, the successful preparation of [Cu(dchtmp)] represents a major step forward for the design and discovery of novel earth-abundant photosensitizers made possible through a newly conceived ligand synthetic strategy.
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http://dx.doi.org/10.1021/acs.inorgchem.1c01242DOI Listing
June 2021

What role for AHR activation in IL4I1-mediated immunosuppression ?

Oncoimmunology 2021 May 12;10(1):1924500. Epub 2021 May 12.

INSERM, IMRB, Univ Paris Est Creteil, Creteil, France.

The amino-acid catabolizing enzyme Interleukin-4 induced gene 1 (IL4I1) remains poorly characterized despite it is emerging as a pertinent therapeutic target for cancer. IL4I1 is secreted in the synaptic cleft by antigen-presenting cells. It inhibits TCR signaling, modulates naïve T cell differentiation and limits effector T cell proliferation. IL4I1 expression in tumors shapes the tumor microenvironment and impairs the antitumor cytotoxic T cell response, thereby facilitating cancer immune escape. Several mechanisms participate in these effects. Recent data suggest a role of new IL4I1 metabolites in activation of the aryl-hydrocarbon receptor (AHR). Here, we observe that expression of IL4I1 is poorly correlated with that of validated targets of AHR in human cancers. Moreover, dendritic cells do not upregulate AHR target genes in relation with IL4I1 expression . Finally, IL4I1 activity toward tryptophan leading to production of AHR-activating products is very low, and should be negligible when tryptophan-degrading enzymes of higher affinity compete for the substrate. We recently showed that IL4I1 expression by dendritic cells directly regulates immune synapse formation and modulates the repertoire and memory differentiation of responding CD8 T cells after viral infection. Thus, IL4I1 may restrain tumor control through regulating the priming of tumor-specific CD8 T cells, independently of AHR activation.
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http://dx.doi.org/10.1080/2162402X.2021.1924500DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8118450PMC
May 2021
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