@article{rosko_wheeler_alameh_faulkner_durand_castellano_2024, title={Enhanced Visible Light Absorption in Heteroleptic Cuprous Phenanthrolines}, volume={63}, ISSN={["1520-510X"]}, url={https://doi.org/10.1021/acs.inorgchem.3c04024}, DOI={10.1021/acs.inorgchem.3c04024}, abstractNote={This work presents a series of Cu(I) heteroleptic 1,10-phenanthroline chromophores featuring enhanced UVA and visible-light-harvesting properties manifested through vectorial control of the copper-to-phenanthroline charge-transfer transitions. The molecules were prepared using the HETPHEN strategy, wherein a sterically congested 2,9-dimesityl-1,10-phenanthrolne (mesPhen) ligand was paired with a second phenanthroline ligand incorporating extended π-systems in their 4,7-positions. The combination of electrochemistry, static and time-resolved electronic spectroscopy, 77 K photoluminescence spectra, and time-dependent density functional theory calculations corroborated all of the experimental findings. The model chromophore, [Cu(mesPhen)(phen)]+ (1), lacking 4,7-substitutions preferentially reduces the mesPhen ligand in the lowest energy metal-to-ligand charge-transfer (MLCT) excited state. The remaining cuprous phenanthrolines (2-4) preferentially reduce their π-conjugated ligands in the low-lying MLCT excited state. The absorption cross sections of 2-4 were enhanced (εMLCTmax = 7430-9980 M-1 cm-1) and significantly broadened across the UVA and visible regions of the spectrum compared to 1 (εMLCTmax = 6494 M-1 cm-1). The excited-state decay mechanism mirrored those of long-lived homoleptic Cu(I) phenanthrolines, yielding three distinguishable time constants in ultrafast transient absorption experiments. These represent pseudo-Jahn-Teller distortion (τ1), singlet-triplet intersystem crossing (τ2), and the relaxed MLCT excited-state lifetime (τ3). Effective light-harvesting from Cu(I)-based chromophores can now be rationalized within the HETPHEN strategy while achieving directionality in their respective MLCT transitions, valuable for integration into more complex donor-acceptor architectures and longer-lived photosensitizers.}, number={3}, journal={INORGANIC CHEMISTRY}, author={Rosko, Michael C. and Wheeler, Jonathan P. and Alameh, Reem and Faulkner, Adrienne P. and Durand, Nicolas and Castellano, Felix N.}, year={2024}, month={Jan}, pages={1692–1701} }
 @article{bateni_sadeghi_orouji_bennett_punati_stark_wang_rosko_chen_castellano_et al._2024, title={Smart Dope: A Self-Driving Fluidic Lab for Accelerated Development of Doped Perovskite Quantum Dots (Adv. Energy Mater. 1/2024)}, volume={14}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.202470001}, abstractNote={Self Driving Lab In article number 2302303,Milad Abolhasani and co-workers present a self-driving lab, called Smart Dope, for the fast-tracked discovery of doped quantum dots (QDs) for applications in clean energy technologies. Smart Dope utilizes machine learning-guided operation of flow reactors integrated with an in-situ characterizationmodule in a ‘closed-loop’ fashion to discover the best-in-class QD within one day of autonomous experiments.}, number={1}, journal={ADVANCED ENERGY MATERIALS}, author={Bateni, Fazel and Sadeghi, Sina and Orouji, Negin and Bennett, Jeffrey A. and Punati, Venkat S. and Stark, Christine and Wang, Junyu and Rosko, Michael C. and Chen, Ou and Castellano, Felix N. and et al.}, year={2024}, month={Jan} }
 @article{rosko_espinoza_arteta_kromer_wheeler_castellano_2023, title={Employing Long-Range Inductive Effects to Modulate Metal-to- Ligand Charge Transfer Photoluminescence in Homoleptic Cu(I) Complexes}, volume={62}, ISSN={["1520-510X"]}, url={https://doi.org/10.1021/acs.inorgchem.2c04315}, DOI={10.1021/acs.inorgchem.2c04315}, abstractNote={Four Cu(I) bis(phenanthroline) photosensitizers formulated from a new ligand structural motif (Cu1-Cu4) coded according to their 2,9-substituents were synthesized, structurally characterized, and fully evaluated using steady-state and time-resolved absorption and photoluminescence (PL) measurements as well as electrochemistry. The 2,9-disubstituted-3,4,7,8-tetramethyl-1,10-phenanthroline ligands feature the following six-membered ring systems prepared through photochemical synthesis: 4,4-dimethylcyclohexyl (1), tetrahydro-2H-pyran-4-yl (2), tetrahydro-2H-thiopyran-4-yl (3), and 4,4-difluorocyclohexyl (4). Universally, these Cu(I) metal-to-ligand charge transfer (MLCT) chromophores display excited-state lifetimes on the microsecond time scale at room temperature, including the three longest-lived homoleptic cuprous phenanthroline excited states measured to date in de-aerated CH2Cl2, τ = 2.5-4.3 μs. This series of molecules also feature high PL quantum efficiencies (ΦPL = 5.3-12% in CH2Cl2). Temperature-dependent PL lifetime experiments confirmed that all these molecules exhibit reverse intersystem crossing and display thermally activated delayed PL from a 1MLCT excited state lying slightly above the 3MLCT state, 1050-1490 cm-1. Ultrafast and conventional transient absorption measurements confirmed that the PL originates from the MLCT excited state, which remains sterically arrested, preventing an excessive flattening distortion even when dissolved in Lewis basic CH3CN. Combined PL and electrochemical data provided evidence that Cu1-Cu4 are highly potent photoreductants (Eox* = -1.73 to -1.62 V vs Fc+/0 in CH3CN), whose potentials are altered solely based on which heteroatoms or substituents are resident on the 2,9-appended ring derivatives. It is proposed that long-range electronic inductive effects are responsible for the systematic modulation observed in the PL spectra, excited-state lifetimes, and the ground state absorption spectra and redox potentials. Cu1-Cu4 quantitatively follow the energy gap law, correlating well with structurally related cuprous phenanthrolines and are also shown to triplet photosensitize the excited states of 9,10-diphenylanthracene with bimolecular rate constants ranging from 1.61 to 2.82 × 108 M-1 s-1. The ability to tailor both photophysical and electrochemical properties using long-range inductive effects imposed by the 2,9-ring platforms advocates new directions for future MLCT chromophore discovery.}, number={7}, journal={INORGANIC CHEMISTRY}, author={Rosko, Michael C. and Espinoza, Eli M. and Arteta, Sarah and Kromer, Sarah and Wheeler, Jonathan P. and Castellano, Felix N.}, year={2023}, month={Feb}, pages={3248–3259} }
 @article{bateni_sadeghi_orouji_bennett_punati_stark_wang_rosko_chen_castellano_et al._2023, title={Smart Dope: A Self-Driving Fluidic Lab for Accelerated Development of Doped Perovskite Quantum Dots}, volume={11}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.202302303}, abstractNote={Metal cation‐doped lead halide perovskite (LHP) quantum dots (QDs) with photoluminescence quantum yields (PLQYs) higher than unity, due to quantum cutting phenomena, are an important building block of the next‐generation renewable energy technologies. However, synthetic route exploration and development of the highest‐performing QDs for device applications remain challenging. In this work, Smart Dope is presented, which is a self‐driving fluidic lab (SDFL), for the accelerated synthesis space exploration and autonomous optimization of LHP QDs. Specifically, the multi‐cation doping of CsPbCl3 QDs using a one‐pot high‐temperature synthesis chemistry is reported. Smart Dope continuously synthesizes multi‐cation‐doped CsPbCl3 QDs using a high‐pressure gas‐liquid segmented flow format to enable continuous experimentation with minimal experimental noise at reaction temperatures up to 255°C. Smart Dope offers multiple functionalities, including accelerated mechanistic studies through digital twin QD synthesis modeling, closed‐loop autonomous optimization for accelerated QD synthetic route discovery, and on‐demand continuous manufacturing of high‐performing QDs. Through these developments, Smart Dope autonomously identifies the optimal synthetic route of Mn‐Yb co‐doped CsPbCl3 QDs with a PLQY of 158%, which is the highest reported value for this class of QDs to date. Smart Dope illustrates the power of SDFLs in accelerating the discovery and development of emerging advanced energy materials.}, journal={ADVANCED ENERGY MATERIALS}, author={Bateni, Fazel and Sadeghi, Sina and Orouji, Negin and Bennett, Jeffrey A. and Punati, Venkat S. and Stark, Christine and Wang, Junyu and Rosko, Michael C. and Chen, Ou and Castellano, Felix N. and et al.}, year={2023}, month={Nov} }
 @article{kim_rosko_dang_castellano_teets_2023, title={Sterically Encumbered Heteroleptic Copper(I) <i>β</i>-Diketiminate Complexes with Extended Excited-State Lifetimes}, volume={10}, ISSN={["1520-510X"]}, url={https://doi.org/10.1021/acs.inorgchem.3c02042}, DOI={10.1021/acs.inorgchem.3c02042}, abstractNote={One of the main challenges in developing effective copper(I) photosensitizers is their short excited-state lifetimes, usually attributed to structural distortion upon light excitation. We have previously introduced copper(I) charge-transfer chromophores of the general formula Cu(N^N)(ArNacNac), where N^N is a conjugated diimine ligand and ArNacNac is a substituted β-diketiminate ligand. These chromophores were promising regarding their tunable redox potentials and intense visible absorption but were ineffective as photosensitizers, presumably due to short excited-state lifetimes. Here, we introduce sterically crowded analogues of these heteroleptic chromophores with bulky alkyl substituents on the N^N and/or ArNacNac ligand. Structural analysis was combined with electrochemical and photophysical characterization, including ultrafast transient absorption (UFTA) spectroscopy to investigate the effects of the alkyl groups on the excited-state lifetimes of the complexes. The molecular structures determined by single-crystal X-ray diffraction display more distortion in the ground state as alkyl substituents are introduced into the phenanthroline or the NacNac ligand, showing smaller τ4 values due to the steric hindrance. UFTA measurements were carried out to determine the excited-state dynamics. Sterically encumbered Cu5 and Cu6 display excited-state lifetimes 15-20 times longer than unsubstituted complex Cu1, likely indicating that the incorporation of bulky alkyl substituents inhibits the pseudo-Jahn-Teller (PJT) flattening distortion in the excited state. This work suggests that the steric properties of these heteroleptic copper(I) charge-transfer chromophores can be readily modified and that the excited-state dynamics are strongly responsive to these modifications.}, journal={INORGANIC CHEMISTRY}, author={Kim, Dooyoung and Rosko, Michael C. and Dang, Vinh Q. and Castellano, Felix N. and Teets, Thomas S.}, year={2023}, month={Oct} }
 @article{chen_pedersen_dow_fayad_hauke_rosko_danilov_blakemore_dechert-schmitt_knauber_et al._2022, title={A Unified Approach to Decarboxylative Halogenation of (Hetero)aryl Carboxylic Acids}, volume={144}, ISSN={["1520-5126"]}, url={https://doi.org/10.1021/jacs.2c02392}, DOI={10.1021/jacs.2c02392}, abstractNote={Aryl halides are a fundamental motif in synthetic chemistry, playing a critical role in metal-mediated cross-coupling reactions and serving as important scaffolds in drug discovery. Although thermal decarboxylative functionalization of aryl carboxylic acids has been extensively explored, the scope of existing halodecarboxylation methods remains limited, and there currently exists no unified strategy that provides access to any type of aryl halide from an aryl carboxylic acid precursor. Herein, we report a general catalytic method for direct decarboxylative halogenation of (hetero)aryl carboxylic acids via ligand-to-metal charge transfer. This strategy accommodates an exceptionally broad scope of substrates. We leverage an aryl radical intermediate toward divergent functionalization pathways: (1) atom transfer to access bromo- or iodo(hetero)arenes or (2) radical capture by copper and subsequent reductive elimination to generate chloro- or fluoro(hetero)arenes. The proposed ligand-to-metal charge transfer mechanism is supported through an array of spectroscopic studies.}, number={18}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, publisher={American Chemical Society (ACS)}, author={Chen, Tiffany Q. and Pedersen, P. Scott and Dow, Nathan W. and Fayad, Remi and Hauke, Cory E. and Rosko, Michael C. and Danilov, Evgeny O. and Blakemore, David C. and Dechert-Schmitt, Anne-Marie and Knauber, Thomas and et al.}, year={2022}, month={May}, pages={8296–8305} }
 @article{gowda_lee_rosko_petersen_castellano_milsmann_2022, title={Long-Lived Photoluminescence of Molecular Group 14 Compounds through Thermally Activated Delayed Fluorescence}, volume={5}, url={https://doi.org/10.1021/acs.inorgchem.2c00182}, DOI={10.1021/acs.inorgchem.2c00182}, abstractNote={Photoluminescent molecules exploiting the sizable spin-orbit coupling constants of main group metals and metalloids to access long-lived triplet excited states are relatively rare compared to phosphorescent transition metal complexes. Here we report the synthesis of three air- and moisture-stable group 14 compounds E(MePDPPh)2, where E = Si, Ge, or Sn and [MePDPPh]2- is the doubly deprotonated form of 2,6-bis(5-methyl-3-phenyl-1H-pyrrol-2-yl)pyridine. In solution, all three molecules exhibit exceptionally long-lived triplet excited states with lifetimes in the millisecond range and show highly efficient photoluminescence (Φ ≤ 0.49) due to competing prompt fluorescence and thermally activated delayed fluorescence at and around room temperature. Temperature-dependent steady-state emission spectra and photoluminescent lifetime measurements provided conclusive evidence for the two distinct emission pathways. Picosecond transient absorption spectroscopy allowed further analysis of the intersystem crossing (ISC) between singlet and triplet manifolds (τISC = 0.25-3.1 ns) and confirmed the expected trend of increased ISC rates for the heavier elements in otherwise isostructural compounds.}, journal={Inorganic Chemistry}, publisher={American Chemical Society (ACS)}, author={Gowda, Anitha S. and Lee, Tia S. and Rosko, Michael C. and Petersen, Jeffrey L. and Castellano, Felix N. and Milsmann, Carsten}, year={2022}, month={May} }
 @article{rosko_wells_hauke_castellano_2021, title={Next Generation Cuprous Phenanthroline MLCT Photosensitizer Featuring Cyclohexyl Substituents}, volume={60}, ISSN={["1520-510X"]}, url={https://doi.org/10.1021/acs.inorgchem.1c01242}, DOI={10.1021/acs.inorgchem.1c01242}, abstractNote={A new long-lived, visible-light-absorbing homoleptic Cu(I) metal-to-ligand charge transfer (MLCT) photosensitizer, [Cu(dchtmp)2]PF6 (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 CH2Cl2 (τ = 2.6 μs, ΦPL = 5.5%), CH3CN (τ = 1.5 μs, ΦPL = 2.6%), and THF (τ = 2.0 μs, ΦPL = 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)2]PF6 is a potent photoreductant (-1.77 V vs Fc+/0 in CH3CN) 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)2]+ represents a major step forward for the design and discovery of novel earth-abundant photosensitizers made possible through a newly conceived ligand synthetic strategy.}, number={12}, journal={INORGANIC CHEMISTRY}, publisher={American Chemical Society (ACS)}, author={Rosko, Michael C. and Wells, Kaylee A. and Hauke, Cory E. and Castellano, Felix N.}, year={2021}, month={Jun}, pages={8394–8403} }