ConspectusGuanidine exhibits both similarities and differences compared to amines, endowing it with unique catalytic properties. The synthesis of chiral guanidine organocatalysts has garnered significant interest, focusing on three primary guanidine backbones: bicyclic, monocyclic, and open-chain structures. Acyclic guanidines, while more synthetically accessible than their cyclic counterparts, present challenges due to their flexible conformations and multiple substitution patterns. Moreover, the potential of chiral guanidine ligands in metal complex catalysis remains largely underexplored.Our research group has been actively exploring chiral guanidine-amide-based asymmetric catalysis since 2009. The design strategy for these catalysts is rooted in the bifunctional capabilities of amino acids, which are easily functionalized into acyclic guanidine amides. These compounds incorporate new Brønsted base units and hydrogen bond donors. The readily tunable structure of guanidine amides allows five forms, including monoguanidine amide (GA), bisguanidine and its hemisalt (GB), guanidine sulfonamide (GC), hybrid guanidine amide-pyridine (GD), and quaternary guanidinium salt (QG). The applications of these compounds in asymmetric catalysis can be driven into four modes based on the role of guanidines: organocatalysis, organo-metal synergistic catalysis, guanidine/transition metal complex catalysis, and phase-transfer catalysis. First, as bifunctional organocatalysts through base/H-bond activation, guanidine derivatives have demonstrated exceptional diastereo- and enantioselectivity in a wide range of reactions including polar addition and cascades, cyclization, substitution, and insertion, etc. In these cases, abundant and labile H-bond interactions from both guanidine and amides account for the high diastereo- and enantioselectivity. Second, the combination of chiral guanidines with achiral dirhodium salts enabled synergistic catalysis to activate the reaction partners simultaneously, where the guanidine unit is disclosed as a proton shuttle or a chalcogen bond acceptor. Third, the copper complexes of guanidine amides and hybrid guanidines could promote both polar and radical reactions. The unique performance of these new catalysts lies in either bifunctional catalysis via a combination of metal coordination and H-bond assistance or rich electronic and coordination properties to leverage the redox ability of the catalytic species. In addition, the quaternary guanidinium salt has emerged as an effective bifunctional phase-transfer catalyst for tackling the challenging enantioselectivity issue in asymmetric α-aromatization of arynes.In this Account, we recount the development of a series of chiral guanidine-amide-based organocatalysts and ligands derived from amino acids. Their applications are meticulously selected from a diverse array of asymmetric reactions, highlighting the evolution of their structures, functionalities, and mechanistic features. Special emphasis is placed on the key factors that contribute to high stereoselectivity in representative catalytic processes.

CRISPR-based sensing platform for the Group B streptococcus screening in pregnant women.

Abstract The disordered crystal growth and undesired degradation of perovskite films limit the further improvement of perovskite solar cells (PSCs) performance and their commercialization. Herein, an in situ modulation strategy is proposed for preparing high-quality and stable perovskite film through adjustment of phase transformation kinetics. Benefiting from the in situ reaction between chloroformamidinium hydrochloride (ClFACl) and FA cations, the impurity intermediate phase in the perovskite film is inhibited and the α-FAPbI3 phase is induced to grow along a preferred (001) orientation. Furthermore, the introduction of ClFACl and in situ formation of guanidinium salts (FA-Gua) strengthen the intermolecular interactions in the interior of crystals, which restrains the α-phase degradation of the as-prepared perovskite films under humid and thermal treatments. With crystal orientation optimization and defects reduction, the PSCs with in situ formed FA-Gua yield a champion efficiency of 25.85% and demonstrate excellent phase stability under long-term thermal and humid ageing conditions. This in situ chemical modulation strategy expands the avenue toward optimization of crystallization orientation and α-phase stabilization, promoting the development of PSCs with enhanced performance and stability.

Electrochemistry allows for the simultaneous conversion of hydrogen sulfide (H2S) to hydrogen (H2) and sulfur, achieving atomic economy, and is a sustainable and cost-effective method. At the same time, an electrolyte with high conductivity and H2S absorption that can effectively capture H2S in an electrochemical process is essential. An ionic liquid electrolyte system for the absorption and electrolysis of H2S was constructed using the guanidine salt ionic liquid with amine-based functional groups as the carrier electrolyte, water as the solvent, and NaOH as the H2S absorber. The prepared electrolyte ([TMG][IM]-AE-30) showed a strong absorption of H2S with an equilibrium solubility of 100.82 g L-1. Under constant potential electrolysis at 1.0 V vs. RHE, the maximum hydrogen production rate reaches 2919.97 μmol h-1 and the Faraday efficiency reaches 99%, and the anodic product is α-sulfur with a production of 0.881 g after electrolysis for 8 h; the current density and hydrogen production rate are still higher than those of the AE systems after three cycles. Overall, the system has good hydrogen sulfide absorption and electrolysis performances, and [TMG][IM] can effectively improve the H2S absorption and electrolysis efficiencies.

Cationic antibacterial polymers for development of bactericidal materials: Strategies, mechanisms, and applications.

Viral transport medium (VTM) is crucial for retaining clinical specimens, such as the virus or its genetic material from the mucus of respiratory tract of coronavirus disease 2019 (COVID-19) suspected patients. However, the locally produced VTM in Indonesia lacks the ability to inactivate the virus, risking the safety of diagnostic personnel. The aim of this study was to formulate inactive VTM (iVTM) incorporating chaotropic agents like guanidine salt, along with anionic detergents, chelators, buffers, and surfactants, to inactivate the virus while maintaining RNA integrity. Viral RNA stability in iVTM (pH 4 and pH 6) was evaluated for 30 days at 4°C and 25–28°C. In vitro inactivation test was performed on SARS-CoV-2 isolate (variant B1). The stability test revealed that storing the clinical specimens in iVTM at pH 6 maintained severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) detectability by qPCR for up to 30 days at cold and room temperatures. Stability assessments conducted over a 4-month period (at 25–28°C) on iVTM with a pH of 6 revealed clear appearance, consistent pH stability, no alteration in the solution color, and no indications of bacterial or fungal contamination. Results from an in vitro inactivation assay demonstrated that iVTM pH 6 eliminated SARS-CoV-2 infectivity within just five minutes of contact. These findings suggest that iVTM pH 6 offers a safer and cost-effective alternative for handling and transportation of clinical specimens.

The asymmetric ring-opening of aliphatic cyclic carbonates represents a strategically important, yet challenging, transformation for accessing chiral building blocks and polymeric materials. Herein, we present a novel methodology enabling the enantioselective desymmetrization of aliphatic cyclic carbonates using morpholine as the nucleophile and chiral bicyclic guanidinium salt as the catalyst under mild conditions. The protocol exhibits exceptional substrate tolerance, providing a diverse array of alkyl- and aromatic-substituted products with excellent yield and high enantioselectivity (97:3). Notably, it also enables the parallel kinetic resolution of racemic unsymmetrical alkyl-substituted cyclic carbonates with superior selectivity. The stereochemical outcome is supported by density functional theory (DFT) studies, which reveal a cooperative mechanism involving chiral guanidinium cation-solvent interactions that stabilize the transition state for the enantioselective 1,3-proton transfer step.

Both molecularly imprinted polymer (MIP) and dummy-imprinted polymer (DIP) sensors were designed and comparatively analyzed for the determination of camostat mesylate (CAM). MIP and DIP sensors were designed with CAM, guanidine (GUA), and dimethylformamide (DMF) as target molecules and para-aminobenzoic acid (p-ABA) as a functional monomer using the electropolymerization (EP) method on the surface of screen-printed gold electrodes (SPAuE). The created sensors' morphological and electrochemical characteristics were examined to verify their construction. Additionally, the alterations on the electrode surface at the molecular and electronic levels were assessed using quantum chemistry calculations. The dynamic linear range of the MIP-based sensors designed under optimized experimental conditions was 2.5 × 10-13-2.5 × 10-12M, while it was 2.5 × 10-12-2.5 × 10-11M and 2.5 × 10-12-5.0 × 10-11M for the DIP-based sensors prepared using GUA and DMF, respectively. The impact of several interfering compounds on the CAM peak current was assessed to determine the selectivity. The RSD and recovery values were computed with 100 times more interfering agents present. The reproducibility of peak current RSD values of poly(Py-co-p-ABA)@CAM@MIP/SPAuE, poly(Py-co-p-ABA)@GUA@DIP/SPAuE, and poly(Py-co-p-ABA)@DMF@DIP/SPAuE sensors were 1.85%, 2.25%, and 2.33%, respectively. In addition, the recovery values ​​of MIP and DIP-based sensors in commercial serum samples were 99.36%, 99.47%, and 100.51%, respectively. The imprinting factor (IF) values were computed for the competitive compounds with comparable chemical structures. The developed sensor was also effectively used to measure CAM in commercial serum samples. In summary, the designed sensors demonstrated highsensitivity, selectivity, repeatability, and reproducibility against the CAM molecule.

CsSnI3 perovskite is a thin-film semiconductor with high intrinsic conductivity for various device applications (thermoelectric, photovoltaics, etc.). Stoichiometric CsSnI3 has high-density defects and structural imperfections affecting device performance. In this work, we made an investigation on A-site cation engineering to evaluate the correlation between structural and transport parameters for effective operation in rectifying devices. Here, we analyzed CsSnI3 thin films modified with methylamine (MA), formamidine (FA), guanidine (GuA), and 5-ammonium valeric acid (AVA) cations, correlating structural parameters obtained by Rietveld refinement with their optoelectronic and diode characteristics. MA-, FA-, and GuA-substituted films exhibited low sheet resistance (∼450–2200 Ω/sq); however, strain-induced lattice distortions and accumulated defects in GuA-substituted films significantly hindered effective charge collection and increased recombination losses. AVA substitution formed low-conductivity 2D interlayers, increasing resistance (>105 Ω/sq) and altering transient response characteristics, yet provided minimal reverse switching losses (∼100 μW/cm2), beneficial for high-frequency applications. FA substitution emerged as optimal, balancing structural stability, conductivity, minimal defects, and relevant diode properties. The obtained results highlight that targeted lattice modifications strongly influence the practical performance of rectifying p–i–n diodes based on CsSnI3.

Guanidinium salt treatments provide a simple yet effective approach to suppress ion migration and stabilize grain boundaries in perovskite solar cells (PSCs). This study investigates the effects of guanidinium halide (GuaX, where X = I, Br, or Cl) surface treatments on PSC performance and stability, addressing challenges related to ion migration and grain boundary instability. Low‐energy electron microscopy reveals that GuaX treatments modulate the work function, reducing it from ~5.44 eV in untreated films to ~4.96 eV in GuaI‐treated films, a change attributed to differences in electronegativity and ionic size. Conductive atomic force microscopy demonstrates improved and uniformed current distribution, particularly in GuaCl‐treated films, owing to GuaCl's ability to mitigate surface and grain boundary defects. Current–voltage mapping highlights GuaCl's role in stabilizing charge transport at grain boundaries. Optimized GuaX treatments substantially enhance photovoltaic performance, with GuaCl‐treated PSCs achieving a power conversion efficiency of 21.10%, an open‐circuit voltage of 1.15 V, and a fill factor of 80.16%. Surface photovoltage analysis further confirms a significant reduction in trap‐state density (from 29–16 meV), while density functional theory calculations indicate that GuaCl exhibits the highest adsorption energy (−2.58 eV), indicating strong interaction with the perovskite. Moreover, stability tests under ambient conditions demonstrate exceptional durability, with GuaCl‐treated PSCs retaining over 95% of their initial efficiency after 60 days.

Functionalized carbon dots with guanidine salt ionic liquid regulate oxidative damage and amyloid aggregation.

Construction of efficient ethylene removal and antibacterial cellulose paper-based packaging materials for avocado preservation.

FOX-7-Fused Bicyclic Guanidinium Salts: A Series of High-Density Insensitive Energetic Materials

Guanidines make up a class of compounds with important applications in catalysis and medicinal chemistry. In this systematic study, we report on the guanylation of aliphatic amines, anilines, (sulfon)amides, ureas, and carbamates by repurposing HATU, a common amide coupling reagent. The products are 2-substituted 1,1,3,3-tetramethylguanidines (TMGs), a group of sterically hindered superbases. The reaction of a guanidinium salt with aliphatic amines has been regarded as an unwanted side-reaction in amide coupling, yet the exact mechanistic details have been unclear. Our mechanistic investigation shows that the guanylation is highly dependent on the nature of the nitrogen nucleophile. Our findings were applied on two fronts: minimizing guanylation in competing amide coupling reactions as well as maximizing guanylation in a simple one-step synthesis of a broad variety of 2-substituted TMGs, including the late-stage functionalization of pharmaceuticals.

Abstract A straightforward, operationally simple and inexpensive one‐pot synthesis of substituted 4‐perfluoroalkyl‐pyrimidine derivatives is reported. Employing triphenylphosphine as a photocatalyst and an additional imidazolidinone organocatalyst, aldehydes undergo α‐perfluoroalkenylation giving highly electron‐deficient enals, which form the heterocycle upon condensation with a guanidinium salt. The method tolerates many functional groups and gives the corresponding products in up to 84 % yield over both steps.

Zwitterionic energetic materials offer a unique combination of high performance and stability, yet their synthesis and stability enhancement remain key challenges. In this study, we report the synthesis of a highly stable (dinitromethyl-functionalized zwitterionic compound, 1-(amino(iminio)methyl)-4,5-dihydro-1H-pyrazol-5-yl)dinitromethanide (4), with a thermal decomposition temperature of 215 °C, surpassing that of most previously reported energetic monocyclic zwitterions (Td < 150 °C). This compound was synthesized via intramolecular cyclization of a trinitromethyl-functionalized hydrazone precursor. Further chemical modifications, including nitration and fluorination, enabled zwitterion-to-zwitterion transformations, resulting in the formation of nitramines 10 and 12. Additionally, the perchlorate salt (8) of 4 was synthesized, along with ammonium (13), guanidinium (14), and potassium (15) salts derived from 10, all retaining zwitterionic properties. Physicochemical evaluations reveal that zwitterion 12 exhibits excellent thermal stability (Td = 181 °C) and an optimal balance between high energy output (detonation velocity: 8329 m s-1, detonation pressure: 29.4 GPa) and reduced sensitivity (impact sensitivity: 35 J, friction sensitivity: 320 N). Notably, potassium salt 15 demonstrates superior thermal stability (Td = 233 °C), exceeding that of RDX. These results expand the design framework for energetic zwitterions and contribute to the development of high-energy, low-sensitivity energetic materials.

Stabilization of n-type carbon nanotubes is achieved by separate n-doping and cation replacement processes utilizing bicyclic guanidinium cation as stabilizer.

Separation of Gold(I) from cyanide-containing wastewater by functional polymer inclusion membrane containing guanidinium ionic liquid

In perovskite solar cells, the presence of stress and defects at interfaces promotes performance degradation and poor stability of the devices. The formation of these defects is more prominent in two-step antisolvent-free perovskite film fabrication. This study addresses these challenges by introducing guanidine sulfate (Gua-S) at the tin oxide/formamidinium lead iodide perovskite interface, fabricated without antisolvent under ambient air. Interfacial Gua-S enhanced morphology by forming bonds between uncoordinated Pb2+ ions and I- vacancies at the interface and showed improvement in the crystallinity and quality of the perovskite film. Microstructural stress analysis indicated a substantial reduction in stress, decreasing from 50.6 to 20.72 MPa with the application of Gua-S. Moreover, the Gua-S treated solar cells showed significant improvements and achieved an open circuit voltage of 1.08 V and 22.34% efficiency. Further, electrochemical impedance spectroscopic analysis showed improved built-in potential, carrier lifetime, and charge recombination lifetime for treated devices. The devices retained over 87% of the initial power conversion efficiency after 2000 hours of operation. This comprehensive study addresses the fundamental issues of interfacial stress and defects in perovskite solar cells and demonstrates the efficacy of Gua-S salt in enhancing both the structural and functional aspects of the antisolvent-free device fabrication process.

Since the proposition of the Hofmeister series, guanidinium (Gdm) salts hold a special mention in protein science owing to their contrasting effect on protein(s) depending on the counteranion(s). For example, while GdmCl is known to act as a potential protein denaturant, Gdm2SO4 offers minimal effect on protein structure. Despite the fact that theoretical studies reckon the formation of ion-pairing to be responsible for such behavior, experimental validation of this hypothesis is still in sparse. In this study, we combine electrochemical impedance spectroscopy (EIS) and THz spectroscopy to underline the effect of GdmCl and Gdm2SO4 on a model amide molecule N-methylacetamide (NMA). Molecular dynamics (MD) simulation studies predict that Gdm2SO4 forms heteroion pairing in water, which inhibits Gdm+ ions to approach NMA molecules, while in case of GdmCl, Gdm+ ions directly interact with NMA. The experimental findings on ion hydration, specifically the detailed analysis of the ion-water rattling mode, which appears in the THz frequency domain, unambiguously endorse this hypothesis. Our study establishes the fact that the propensity of ion-pairing in Gdm salts dictates their (de)stabilization effect on proteins.