About

Phil Castellano is a Professor and the Goodnight Innovation Distinguished Chair at NC State University, affiliated with the Department of Chemistry. He holds a Ph.D. in Chemistry from Johns Hopkins University, earned in 1996, and a B.A. in Chemistry from Clark University. His current research focuses on areas including metal-organic chromophore discovery, photophysics, energy transfer, photochemical upconversion, solar fuels photocatalysis, energy transduction at semiconductor/molecular interfaces, excited state electron transfer, ultrafast phenomena, and next-generation OLED technologies. Castellano is involved in various research groups related to analytical, energy, inorganic, and physical chemistry, and he is a co-director of the Organic and Carbon Electronics Cluster. His work emphasizes understanding and developing advanced materials and processes for energy and electronic applications.

Selected publications

• CCDC 2503159: Experimental Crystal Structure Determination

  The Cambridge Structural Database · 2026-05-08

  datasetOpen access

  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.

  PublisherDOI

• Hot-Carrier Injection and Millisecond Charge Separation from a Robust Heteroleptic Iron(II) Chromophore Immobilized on TiO ₂

  Journal of the American Chemical Society · 2026-05-07

  articleOpen access

  The synthesis, spectroscopic characterization, computational analysis, and photoelectrochemical behavior of a new iron-based chromophore, [(Cpy)2Fe(deeb)](PF6)2 (Fe(Cpy)2(deeb)), where Cpy is 1-methyl-3-(2-pyridyl)imidazole and deeb is 4,4’-(CO2CH2CH3)2-2,2’-bipyridine, is reported. Electrochemically reversible waves assigned to a metal-centered Eo(FeIII/II) = +0.48 and a ligand-centered Eo(Fe2+/+) = −1.47 V vs Fc+/0 reduction were evident in cyclic voltammetry measurements. The combination of a strong σ-donor and a π-acceptor lowered the energy of the metal-to-ligand charge-transfer (MLCT) excited state relative to the metal-centered state. Two MLCT transitions appear in the visible region at 424 and 580 nm. TDDFT calculations revealed that the lower-energy band was well formulated as Fe(II)→deeb, and the higher-energy transition was charge transfer to both the deeb and Cpy ligands. Resonance Raman spectroscopy supports these findings showing enhanced deeb vibrational modes with 532 nm excitation, both deeb and Cpy modes with 473 nm excitation, and exclusively Cpy with 405 nm excitation. Ultrafast spectroscopy reveals a short-lived (∼2 ps) MLCT excited state and a longer-lived (∼20 ps) metal-centered state. Efficient methods to deprotect the ester groups and anchor the complex to mesoporous TiO2 (anatase) thin films in high surface coverages, Fe(Cpy)2(dcb)|TiO2 σ = 3 × 10–8 mol/cm2, were established. Pulsed light excitation of Fe(Cpy)2(dcb)|TiO2 resulted in rapid excited state injection (kinj > 108 s–1) and formation of a charge-separated state, FeIII(Cpy)2(dcb)|TiO2(e), which persists on the millisecond time scale before returning cleanly to the ground state with second-order kinetics. Injection yields measured 50 ns after light excitation were found to double from Φ = 0.15 with green (532 nm) light to 0.30 with blue (457 nm) light excitation. Incident photon-to-current efficiency (% IPCE) measurements as a function of excitation wavelength in a 0.5 M LiI/I2/CH3CN electrolyte provide clear evidence for band-selective “hot carrier” injection from the remote Cpy-localized excited state. Collectively, the spectroscopic and photoelectrochemical data indicate that a semiconductor can intercept hot electrons from iron chromophores even when the excited-state dipole is oriented away from the surface-anchoring ligand.

  PublisherDOI

• Photochemically Triggered Para-Hydrogen-Induced Polarization in a Diplatinum Trihydride Complex

  ChemRxiv · 2026-04-02

  articleOpen accessSenior author

  Transition metal complexes containing platinum(II) are of substantial interest for their rich photophysics, biomedical applications, and catalytic function. Nuclear magnetic resonance (NMR) spectra of the spin-1/2 isotope, 195 Pt, offer detailed insights into the molecular structures of closed-shell Pt(II) complexes, including solvent effects. However, the sensitivity of 195 Pt NMR is mediocre, and its NMR spectra are typically complex. As a result, 1 H NMR spectra are used as the primary characterization tool for Pt(II)-based molecules, relying on J -coupling to the 195 Pt nucleus to provide structural information from the resulting satellite peaks. In efforts to significantly improve the information content from 1 H NMR spectroscopy in a Pt(II)-containing molecule, we utilize [Pt 2 H 2 (μ-H)(μ-dppm) 2 ]PF 6 , where dppm is bis(diphenylphosphino)methane, and leverage its established photoactivity with UV light and H 2 for para-hydrogen-induced polarization (PHIP) to enhance the resultant NMR signals, revealing numerous 195 Pt J-couplings. Moreover, we investigate direct solvent hyperpolarization effects, as well as the indirect effects of solvent on the various observed J -coupling constants in the Pt species, demonstrating correlations with both Lewis basicity and dielectric constant.

  PublisherOA PDFDOI

• Near-Infrared Photoluminescence from Spin-Flip Excited States of π-Conjugated Tris(quinolinolate) Chromium(III) Complexes

  Inorganic Chemistry · 2026-05-20

  articleSenior authorCorresponding

  Tuning metal–ligand covalency offers promising design strategies to tailor the photoluminescence (PL) emission energies of metal-centered, spin-flip excited states. Herein, we report a series of tris(quinolinolate) chromium(III) complexes that exhibit record-low near-infrared II emission energies in a fluid solution at room temperature, afforded by their strong metal–ligand covalencies. Appending π-conjugated arylethynyl substituents to quinolinolate ligands resulted in minimal changes to metal–ligand bond lengths, facilitating nearly indiscriminate metal–ligand covalencies for each tris(quinolinolate) chromium(III) complex. As a result, near-infrared II emission was observed across the series, while simultaneously affording careful tuning of the 4LMCT/4(1ILCT) electronic transition energies across the visible region. Detailed analyses of ground-state electronic structures and excited-state electronic transitions revealed that PL arises from a ligand-field, 2E excited state, admixed with charge-transfer character. This assignment was supported by solvent-dependent near-infrared emission energies and long excited-state lifetimes, consistent with spin-forbidden relaxation (ranging from 115 ± 5 to 123 ± 1 ns across the series). Utilizing spectroscopic data, ligand-field parameters were quantified, further rationalizing the role of strong metal–ligand covalency in enabling near-infrared II emission. Supported by these results, this study presents a new class of ligands that enable room-temperature near-infrared II emission in chromium(III)-based spin-flip excited states.

  PublisherDOI

• Correction to “Varying Diphosphine Bridge Length in Cyclometalated Platinum(II) Dimers Tunes Photophysics by Modulating Orbital Overlap”

  Inorganic Chemistry · 2026-01-16

  articleSenior author
  PublisherDOI

• Synthesis of Ni(II) CNC-Pincer Catalysts with Electronic Donor or Acceptor Groups for Visible Light Driven Carbon Dioxide Reduction

  ChemRxiv · 2026-05-24

  article

  A durable catalytic system is necessary to reduce CO 2 and transform it into useful products. Our catalysts contain Ni(II) bound to CCN pincer ligands composed of N-heterocyclic carbene and pyridine donors. These CNC pincers have electron-donating or -withdrawing substituents on the pyridine ring giving three complexes: Ni R wherein R = NMe 2 , NPh 2 , or CF 3 . These three compounds are also compared with our previously reported Ni H complex (R = H) to examine a compound that is electronically intermediate. A combination of spectroscopic and crystallographic techniques were used to characterize these complexes. A p K a value of -2.7 was determined for protonation of the NMe 2 substituent within Ni NMe2 by 1 H-NMR studies in DMSO-d 6 , and this value aligned well with DFT studies and electrostatic potential surface maps before and after protonation. The study of photocatalytic CO 2 reduction was performed for three complexes in both the presence and absence of an external photosensitizer (PS). Formate (HCO 2 - ) is the major product in the presence of external PS for all these complexes. With a PS, complex Ni NMe2 is the most active photocatalyst for CO formation (TON = 60), where catalysts Ni CF3 and Ni NMe2 are the most active catalysts for formate production (TON = 780 and 750, respectively). The catalysts also perform well as self-sensitized catalysts without external photosensitizer present and produce only formate (TON as high as 220 for Ni NMe2 ). Cyclic voltammetry was used to study the electrochemical properties of each complex under N 2 and CO 2 atmospheres and have revealed that two electrons must be transferred before catalysis ensues. The excited state lifetimes of the complexes were determined by transient absorption spectroscopy (TAS) measurements. This data suggests that all of the new catalysts have excited states that persist for 26-59 ps and that these excited states are likely responsible for diffusional photochemistry involved in CO 2 reduction.

  PublisherDOI

• CCDC 2521374: Experimental Crystal Structure Determination

  The Cambridge Structural Database · 2026-03-27

  datasetOpen accessSenior author

  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.

  PublisherDOI

• CCDC 2521375: Experimental Crystal Structure Determination

  The Cambridge Structural Database · 2026-03-27

  datasetOpen accessSenior author

  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.

  PublisherDOI

• Deciphering the excited-state landscape of Cr( <scp>iii</scp> ) tris(diimines) using [Cr(phen) ₃ ] ³⁺

  Inorganic Chemistry Frontiers · 2026-01-01

  articleOpen accessSenior author

  Ultrafast transient absorption spectroscopy and multiconfigurational calculations (RASSCF) map the excited-state landscape of Cr( iii ) tris(1,10-phenanthroline), providing assignments of the spin-flip dynamics and doublet state absorption.

  PublisherDOI

• Enhanced MMLCT character in thiol-bridged Pt( <scp>ii</scp> ) dimers featuring tridentate cyclometalating ligands

  Dalton Transactions · 2026-01-01

  articleOpen accessSenior author

  MMLCT excited state in 2-5 was observed with a shortened time constant of ∼55 ps, which subsequently relaxes on the timescale of 2-7 ns, atypical for these triplet charge transfer excited states.

  PublisherOA PDFDOI

Labs

• Castellano GroupPI

Awards & honors

• Goodnight Innovation Distinguished Chair
• AAAS Fellow