In-operando electrospray ionization mass spectrometry (ESI-MS) is a powerful tool for investigating reaction mechanisms by monitoring ions directly from the reacting solution in real time. However, observations based on m/z alone often do not constrain mechanistic assignments uniquely. Here we examine the interpretive limits of in-operando ESI-MS using copper-mediated carboxylation chemistry as a case study. Complementary characterization by collision-induced dissociation (CID), threshold CID energetics, infrared multiple-photon dissociation spectroscopy, and density-functional theory reveals that the dominant ion corresponds to an N-bound Cu-benzoxazole resting adduct rather than the Cu-C2 intermediate crystallographically characterized under stoichiometric conditions. Reinterpretation of the observed ions in light of these constraints establishes that the N-bound adduct is the genuine entry point into the productive catalytic cycle, and that the Cu-C2 intermediate-while chemically competent-does not accumulate under catalytic conditions, consistent with the principle that the most readily isolable intermediate is not necessarily the kinetically relevant one. This case study demonstrates that structural and energetic constraints are essential when using in-operando ESI-MS to investigate reaction mechanisms.

Gas-phase ligand dissociation energies of Cu(I) bis(oxazoline) complexes exhibit large and persistent discrepancies between experiment and theory. These deviations have been interpreted as fundamental limitations of density-functional and correlated wave function approaches, despite the absence of direct structural validation of the experimentally probed ions. Here, we show, using infrared multiple-photon dissociation (IRMPD) spectroscopy, trapped ion mobility spectrometry, and electronic-structure calculations, that the mass-selected (S,S-Ph-BOX)2Cu+ ion is not a single, well-defined species. Instead, the IRMPD spectrum previously attributed to (S,S-Ph-BOX)2Cu+ arises from a composite of at least two Cu-containing ions that fall within the same nominal isolation window. Trapped ion mobility spectrometry resolves these contributions and enables acquisition of IR spectra for each species individually. The mobility-selected spectra demonstrate that only one ion corresponds to a genuine bis-chelated Cu(I)-BOX complex, whereas the second species differs in composition by one hydrogen atom and has substantially higher bond dissociation energy. Its presence in the original precursor population would have raised, not lowered, the apparent experimental threshold, confirming that the discrepancy between experiment and theory is genuine. This discrepancy is attributed to systematic overestimation of noncovalent interligand interactions by dispersion-corrected DFT, consistent with the behavior documented for structurally related organometallic systems. The present study underscores the necessity of explicit precursor characterization before thermochemical benchmarks are accepted, and identifies the treatment of noncovalent interactions as the key remaining challenge for computational methods applied to this class of complexes.

Monolithic perovskite/silicon tandem solar cells (PSTSCs) encounter interfacial challenges on textured or semiplanar silicon. Conventional high-performance self-assembled monolayers (SAMs), such as Me-4PACz, suffer from poor wettability, necessitating the use of NiO x interlayers to enable perovskite coating; however, this compromises the fill factor (FF) and open-circuit voltage (V OC). Although highly hydrophilic alternatives like MPA-CPA SAM improve wettability, they still limit device efficiency. Here we introduce a tripodal triazatruxene-based SAM, 3PATAT-C3, engineered to overcome both limitations. Its unique tripodal structure, featuring three phosphonic acid anchors, ensures uniform, defect-free coverage on semiplanar substrates and promotes a face-on molecular orientation that enables pi-orbital overlap with the perovskite film, resulting in exceptional hole extraction and suppressed recombination without the need for NiO x . Despite exhibiting only moderate wettability, 3PATAT-C3 achieved a power conversion efficiency (PCE) of 31.77%. This significantly outperforms both the wettability-compromised NiO x /Me-4PACz benchmark (27.41%) and the highly hydrophilic MPA-CPA SAM (26.28%). This work highlights tripodal molecular design as a transformative strategy for simultaneously optimizing electronic interface quality and processability for high-efficiency semiplanar tandem solar cells.

This study proposes a novel direct X-ray detector that integrates lead-free, fully inorganic Cs3Bi2I9 perovskite with a gap-type metal-semiconductor-metal (MSM) structure. The primary advantage of the proposed device lies in its ultrathin Cs3Bi2I9 perovskite active sensing layer, with a thickness of approximately 350 nm. Compared with conventional photodiode-based X-ray detectors (e.g., Cs3Bi2I9 or amorphous selenium (a-Se) photodiodes), the thickness is reduced by approximately three orders of magnitude, thereby significantly enhancing the feasibility of pixel miniaturization. Experimental results demonstrate that, owing to the internal gain effect induced by the light-induced barrier lowering (LIBL) mechanism, the detector achieves an X-ray sensitivity as high as 4.83 & times; 104 mu C Gy-1 cm-2 and a detection limit as low as 65 nGy s-1 . From a structural design perspective, the gap-type MSM structure exhibits high compatibility with mature thin-film transistor (TFT) fabrication processes, enabling lowcost manufacturing and further reduction in pixel size. Moreover, by minimizing the effective sensing area and integrating a direct-readout pixel configuration, this proposed detector architecture demonstrates strong potential for achieving ultrahigh spatial resolution (e.g., a pixel pitch of 32 mu m). Overall, the device presented in this study provides a viable technological pathway for next-generation applications in high-resolution medical diagnostics, industrial nondestructive testing, and security screening, offering a compelling combination of low cost, environmental friendliness, and high performance.

A synthetic procedure for the preparation of isocyanide cyclopentadienone iron complexes using the corresponding tricarbonyl complexes and primary amines as starting materials is described. By transforming the primary amines into deprotonated phosphoramidates or silyl amines, the CO ligands can be replaced by CNR ligands by abstracting the CO oxygen atom and replacing it with an NR fragment, with concomitant formation of phosphates or silanols as the thermodynamic driving force. The phosphoramidate route, using RNHP(O)(OEt)2, works well for R = alkyl, but fails for R = aryl, presumably due to the reduced nucleophilicity of the intermediate deprotonated phosphoramidate. Aromatic isocyanide ligands are accessible by using silyl amines ArNHTMS (Ar = aryl, TMS = trimethylsilyl) instead. The disclosed procedure has the advantage that the free isocyanide ligands themselves do not need to be isolated, which circumvents the use of strongly unpleasant smelling chemicals. Catalytic transfer hydrogenation reactions show that, under the same reaction conditions, the monoisocyanide complexes perform significantly worse than the corresponding tricarbonyl complexes. Kinetic monitoring revealed that fast catalyst decomposition is responsible for the lower performance. The reaction mechanism of the C equivalent to O/C equivalent to NR transformation was additionally investigated by DFT calculations.

Calculating accurate free energies for solution-phase reactions is notoriously difficult. In our previous joint experimental and computational studies, we observed a striking failure of quantum mechanical calculations with popular implicit solvent models to even qualitatively reproduce the experimental trends of dissociation free energies of numerous proton-bound pyridine dimers in organic solvents [Pollice, R. . J. Am. Chem. Soc. 2017, 139(37), 13126-13140]; [Pollice, R. . Angew. Chem., Int. Ed. 2019, 58(40), 14281-14288]. In this article, we expand the computational study of the dissociation of proton-bound pyridine dimers in the gas phase and in dichloromethane (DCM). In an effort to determine the prerequisites for reproducing the experimental trends and magnitudes of the dissociation free energies (ΔGdiss) in solvent, we investigated the impact of accounting for the ensemble free energy, umbrella sampling, thermodynamic integration, and explicit solvation using semiempirical quantum mechanics and molecular mechanics. We estimated the effect of conformational free energy contributions with semiempirical quantum mechanics (SE). Molecular dynamics (MD) with explicit solvation and classical molecular mechanics (MM) was used as a method to treat not only the solute but also the solvent configurational entropy. We found that explicit solvation with MM is indeed capable of reproducing ΔGdiss in DCM for our test system within an acceptable error margin. We analyze and discuss the results and limitations of our approach for calculating the solvation free energy.

A solution of six-coordinate [Mn(PS2)2] (1) is inert towards nitric oxide (NO) at room temperature. In the presence of a proton source such as p-toluenesulfonic acid or perchloric acid, however, the treatment of 1 with NO in the dark leads to the formation of {MnNO}6 [Mn(NO)(SPS-SPS)] (2) with a metal-diaryldisulphide ligand, as confirmed by several spectroscopy investigations, including single-crystal X-ray diffraction. A possible pathway for the formation of 2 was determined through theoretical studies and involves the following: (i) the thiolato sulphur in 1 interacts with H+ to generate an intermediate [Mn(PS2)(PS2H)]+ (A) with an S⋯H interaction; (ii) the reaction of A with NO yields HNO and an Mn(IV)-bound-thiyl radical species (B); and (iii) the nucleophilicity of the thiyl radical B to an adjacent thiolato sulphur produces a five-coordinate Mn(III)-diaryldisulphide species (C), which reacts with the generated HNO to yield 2. Complex 2 is sensitive to visible light. When photolysis of 2 in solution is performed, complex 1 is regenerated and NO is released, which is related to metal-disulphide/metal-thiolate interconversion.

We report a systematic investigation of noncovalent interactions-particularly an intramolecular hydrogen bond and London Dispersion forces-in singly protonated bis-pyridines, studied across solution and crystalline states. Building on our previous gas-phase study, we combine variable-temperature 1H NMR spectroscopy, single-crystal X-ray diffraction, and density functional theory (DFT) calculations. The measured 1H NMR chemical shifts of the acidic proton serve as a solution-phase structural readout, which we correlate with an independent crystallographic metric. By systematically varying the linker (-CH2-, -O-, and -CH2CH2-) and the pendant substituents (H, methyl, tert-butyl), we examine how increasingly bulky "dispersion energy donors" affect both the intramolecular hydrogen bond and the accessible conformational states. In reference systems, where a single noncovalent interaction governs the geometry, even relatively simple computational models correctly reproduce the experimentally observed structures. However, for molecules featuring two competing noncovalent interactions, the tested, dispersion-corrected, DFT often fails to predict the relative energies of accessible conformers accurately, highlighting current limitations in predictive accuracy. We briefly discuss broader implications of currently achievable predictive accuracy for homogeneous catalysis.

Schematic measurement of bifacial illumination with simulated scenarios of clear sky, overcast sky, and indoor conditions.

Measurement of the formal, gas-phase, d8-d10 bond dissociation energy across a series of structurally homologous heterobimetallic complexes of Pd(II) with Cu(I), Ag(I), Au(I), and Zn(II), themselves models for the transition states for transmetalation in Sonogashira and Negishi couplings, finds large discrepancies relative to predictions by a commonly used dispersion-corrected density-functional theory method, DFT-D3(BJ), but not in all cases. Control studies on the threshold collision-induced dissociation (T-CID) of electrosprayed molecular ions, as well as the deconvolution of the bond energy from the experimentally measured energy-resolved cross sections, indicate that the experimentally determined bond dissociation energies are most likely correct, which raises the question of why the computational methods, while sometimes agreeing acceptably with experiment, can also sometimes disagree egregiously. While initial attempts to characterize the discrepancy focused on the metal-metal interaction, the most likely origin of the discrepancy appears to be an uneven treatment of nonbonded interactions, among them medium-ranged correlation effects and London dispersion, between the ligands on the two metal centers. The contribution of these effects to the formal bond dissociation energy is large enough to be chemically significant, but it appears to depend on the nature of the interacting groups, specifically the hybridization at carbon, and, more importantly, their relative orientation. Whereas face-to-face aryl-aryl interactions seem to be modeled well by PBE-D3(BJ), a representative DFT-D3 method, alkyl-aryl, and edge-to-face aryl-aryl interactions appear to be overestimated. The consequences for structure and stability in organic and organometallic molecules are discussed, especially with regard to relative energies of conformers and interconverting valence isomers.

Protonation and tautomerization significantly impact the conformational landscape and non-covalent interactions in bis(oxazoline) (BOX) ligands, which are crucial for their applications in catalysis. These interactions influence properties such as binding affinity and catalytic efficiency. While tautomerization has been reported for neutral BOX ligands, its role in protonated forms remains less understood. Here we report the structural and spectroscopic characterization of (S,S-Ph-BOX)H+ and its tautomerization-resistant derivative (S,S-Ph-diMeBOX)H+. We show through IRMPD spectroscopy and TIMS experiments, combined with DFT calculations that (S,S-Ph-BOX)H+ is present in its tautomeric form, while a broader conformational landscape is observed for (S,S-Ph-diMeBOX)H+, in which an N-H & sdot;& sdot;& sdot;N proton-shared conformer is identified. These findings provide a deeper understanding of the relationship between tautomerization and non-covalent interactions in protonated BOX ligands, offering insights for the design of catalytic systems.

We report spectroscopic and spectrometric experiments that probe the London dispersion interaction between tert-butyl substituents in three series of covalently linked, protonated bis-pyridines in the gas phase. Molecular ions in the three test series, along with several reference molecules for control, were electrosprayed from solution into the gas phase and then probed by infrared multiphoton dissociation spectroscopy and trapped ion mobility spectrometry. The observed N-H stretching frequencies provided an experimental readout diagnostic of the ground-state geometry of each ion, which could be furthermore compared to a second, independent structural readout via the collision cross section. In each of the three series, the strength of a London dispersion interaction could be modulated systematically by a progressive increase in the size of substituents from H to Me to tert-Bu. Parallel to the experimental study, extensive dispersion-corrected density functional theory (DFT-D3BJ) calculations were performed with a range of exchange correlation functionals. A full analysis of the conformational space for the flexible members of the series, and an analysis of the vibrational spectra in the context of a general double-well potential, finds that DFT-D3BJ appears to significantly overbind alkyl-alkyl interactions, specifically interactions between tert-Bu groups, even failing to predict the minimum energy structures reliably in the case of molecules in which London dispersion competes with other noncovalent interactions such as hydrogen bonding.

Perovskite solar cells approach the efficiency of Si devices but remain limited by ion-migration-driven instability. Here we show that steric tuning of the A-site cation, CsPb(I0.85Br0.15)3 -> FA0 .78Cs0.22Pb(I0.85Br0.15)3 -> FA0.765MA0.15Cs0.085Pb(I0.85Br0.15)3 -> 1% DMA+-doped FA0.765MA0.15Cs0.085Pb(I0.85Br0.15)3, systematically suppresses photoinduced halide migration. In-situ photoluminescence spectra reveal reduced red-shift with increasing tolerance factor, while operando electrochemical impedance spectroscopy under AM 1.5G decouples recombination and ionic transport. The activation energy extracted from Warburg admittance rises from 0.037 to 0.199 eV, and heat-accelerated recombination is mitigated across devices. Under continuous illumination at 300 K, unencapsulated cells retain performance more effectively, with a 54% improvement in operational stability for the DMA+-doped device. Our results provide a composition-agnostic guideline: A-site steric expansion elevates the migration barrier, limits light/heat-driven stoichiometric drift, and stabilizes device operation.

The dual roles of pseudohalide formate anions (HCOO-), acting as both additives and substituents in perovskite solar cells (PSCs), are investigated and compared. An excess amount of CsHCOO added to the FA0.9Cs0.1PbI3 perovskite, serving as an additive, enhances the photovoltaic performance of PSCs. We observed a significant enlargement of perovskite grain size, improved perovskite crystallinity, preferred facet alignment perpendicular to the substrate, and reduced PbI2 formation after incorporating the CsHCOO additive into the perovskite film. This was achieved by slowing the perovskite growth rate through formate-iodide anion exchange. Moreover, the strong coordination between the formate anion and Pb2+ inhibits the formation of metallic Pb0 on the perovskite film surface, passivating surface defects. Benefiting from these improvements, reduced trap density and surface defect passivation lead to suppressed carrier recombination and longer carrier lifetimes. Incorporating 3 mol% CsHCOO additive in n-i-p structured PSCs improves the power conversion efficiency (PCE) from 17.12% to 18.57%, compared to PSCs without CsHCOO. Additionally, CsHCOO-added PSCs exhibited superior ambient stability, retaining 90% of their original PCE after 1000 hours in a 25 +/- 5% relative humidity environment without encapsulation. For the p-i-n structured PSCs, 3 mol% CsHCOO additive enhanced the device PCE to 20.04%, outperforming the device without the CsHCOO additive (PCE = 18.01%). In contrast, substituting CsI with CsHCOO in the perovskite active layer, with a nominal formula of FA0.9Cs0.1PbI3-x(HCOO)x (x = 0.03 and 0.1), induced significant PbI2 formation and non-uniform perovskite films, resulting in reduced PSC performance. Our findings highlight the pivotal role of CsHCOO as an additive in enhancing PSC performance by addressing various challenges related to perovskite film quality and device stability.

Three cyano-coordinated cobalt porphyrin dimers were synthesized and thoroughly characterized. The X-ray structure of the complexes reveals that cyanide binds in a terminal fashion in both the anti and trans isomers of ethane- and ethylene-bridged cobalt porphyrin dimers, while in the cis ethylene-bridged dimer, cyanides bind in both terminal and bridging modes. The nonconjugated ethane-bridged complex stabilizes exclusively a diamagnetic metal-centered oxidation of type CoIII(por)(CN)2 both in the solid and in solution. In contrast, the complexes with the conjugated ethylene-bridge contain signatures of both paramagnetic ligand-centered oxidation of the type CoII(por•+)(CN)2 and diamagnetic metal-centered oxidation of type CoIII(por)(CN)2 with the metal-centered oxidized species being the major component in the solid state as observed in XPS, while the ligand-centered oxidized species are present in a significant amount in solution. 1H NMR spectrum in solution displays two set of signals corresponding to the simultaneous presence of both the diamagnetic and paramagnetic species. EPR and magnetic investigation reveal that there is a moderate ferromagnetic coupling between the unpaired electrons of the low-spin CoII center and the porphyrin π-cation radical in CoII(por•+)(CN)2 species as well as an antiferromagnetic coupling between the two CoII(por•+) units through the ethylene and CN bridges.

Lead halide perovskites applied for solar cells have gained significant attention due to their rapid growth power conversion efficiency. However, its intrinsic instability, stemming from its ionic nature, hampers the...

The Ni(0) methyl complex MeNiGaL was prepared and characterized by XRD, H-1 NMR, C-13 NMR, P-31 NMR, ESI-MS, and UV-vis. The compound can be prepared from the 16-valence electron complex NiGaL by addition of MeLi, yielding the corresponding lithium salt. NiGaL is a close derivative of a complex that has been previously reported by Lu et al. The title compound represents a rare example of a Ni(0) alkyl complex. The complex is based on a bimetallic, tripodal framework featuring a Ni-Ga bond. The methyl complex, isolated as its Li(THF)(4) salt, shows no interaction between the lithium cation and the methyl anion in the solid state. UV-vis titration experiments indicate reversible dissociation of MeLi in solution. Attempts to prepare the corresponding neopentyl or CH2EMe3 complexes (E = N, P), as possible intermediates or analogues thereof in the nickel catalyzed cyclopropanation of unactivated alkenes with NMe4OTf/BuLi, were unsuccessful.

The reason for the discrepancy in reaction rate in hydrogenation reactions using cyclopentadienone iron complexes as catalysts, depending on the absence or presence of a negative charge-tag (sulfonate or phosphonate), was investigated experimentally. Based on NMR and kinetic experiments, the direct binding of the charge-tag to the active site of the catalyst and electric field effects influencing transition state energies could be excluded. Preactivation of the catalysts as the monoacetonitrile dicarbonyl complexes was found to be superior to the in situ activation of the tricarbonyl complex with trimethylamine oxide with an up to 32-fold rate enhancement. CO ligand removal from the tricarbonyl iron complexes with Me3NO was found to be disfavored in protic solvents compared to polar, aprotic solvents. Micelle formation was observed for the negatively charge-tagged complexes, with critical micelle concentrations in the range of 1.75–17 mM depending on the alkali metal counterion. The presence of the tertiary amine moiety in the charge-tagged catalyst was found to be responsible for the decrease in reaction rate. The presence of micelles was found to increase the reaction rate compared to noncharged complexes bearing a tertiary amine group.

Cryogenic ion vibrational predissociation (CIVP) spectroscopy is an established and valuable technique for molecular elucidation in the gas phase. CIVP relies on tunable lasers, wherein among typical laser schemes, the application of mid-infrared continuous-wave quantum cascade laser (cw-QCL) is the most robust and elegant solution, as we have recently demonstrated. However, potential challenges arise from an inhomogeneous character across laser power tuning curves. A large laser power output could have undesired consequences, such as multiphoton absorption or saturation effects. Significant variations in laser power tuning curves could potentially alter the shape of the investigated band, particularly for diffuse bands. In this study, we have developed and introduced an automatic variable laser power attenuator designed to keep the laser power output uniform at a user-defined value across the entire available spectral range. We demonstrated the application of this attenuator in obtaining CIVP spectra of a model compound with a diffuse N-H-N band. This approach enhances the reliability of measuring diffuse bands and overall applicability of cw-QCL.