MDPI - Publisher of Open Access Journals

19 pages, 2722 KiB

Open AccessArticle

Fluorene-Containing β-Diketonato Ligands and Their Rhodium(I) Complexes—A Characterization and Crystallographic Study

by Frederick Jacobus Francois Jacobs, Siyanda Khoza and Eleanor Fourie

Inorganics 2025, 13(8), 255; https://doi.org/10.3390/inorganics13080255 - 30 Jul 2025

Viewed by 221

The highly fluorescent fluorene group is of interest for its unique optical and electronic properties. By incorporating it into a metal complex, these properties are extended to the complex and are useful in a number of different applications. Four β-diketone ligands were synthesized [...] Read more.

The highly fluorescent fluorene group is of interest for its unique optical and electronic properties. By incorporating it into a metal complex, these properties are extended to the complex and are useful in a number of different applications. Four β-diketone ligands were synthesized containing the fluorene-functional group, where the varying substituent on the β-diketone was CF₃ (1), PhCF₃ (2), Ph (3) and PhCH₃ (4). The corresponding cyclooctadiene rhodium(I) complexes of the type [Rh(cod)((fluorene)COCHCOR)], with R = CF₃ (5), PhCF₃ (6), Ph (7) and PhCH₃ (8) were also synthesized. A crystal structure determination of 2 and 6 was performed, highlighting important changes in the ligand structure as a result of metal complexation. The structure of 2 also showed a hydrogen interaction between the hydroxy and carboxyl groups, forming a pseudo six-membered ring that stabilizes the enol form of the compound. Cyclic voltammetry (CV) of the β-diketones 1–4 showed a reduction wave for the reduction of the β-diketonato backbone between −1500 mV and −2100 mV as measured against ferrocene (FcH). CVs of rhodium(I) complexes 5–8 showed a reduction of the β-diketonato backbone between −1800 and −2000 mV, as well as an oxidation wave for the oxidation of the rhodium(I) metal centre at approximately 300 mV. Full article

► Show Figures

Graphical abstract

14 pages, 5036 KiB

Open AccessArticle

Intermolecular Charge Transfer Induced Sensitization of Yb³⁺ in β-Diketone Coordination Compounds with Excellent Luminescence Efficiency

by Trofim A. Polikovskiy, Daniil D. Shikin, Vladislav M. Korshunov, Victoria E. Gontcharenko, Mikhail T. Metlin, Nikolay P. Datskevich, Marat M. Islamov, Victor O. Kompanets, Sergey V. Chekalin, Yuriy A. Belousov and Ilya V. Taydakov

Int. J. Mol. Sci. 2025, 26(14), 6814; https://doi.org/10.3390/ijms26146814 - 16 Jul 2025

Viewed by 234

Abstract

Achieving high quantum yields for Yb³⁺ ion emission in complexes with organic ligands is a challenging task, as most Yb³⁺ complexes with such ligands typically exhibit efficiencies below 3.5%. Our research demonstrates that the introduction of heavy atom-containing ancillary ligands, such [...] Read more.

Achieving high quantum yields for Yb³⁺ ion emission in complexes with organic ligands is a challenging task, as most Yb³⁺ complexes with such ligands typically exhibit efficiencies below 3.5%. Our research demonstrates that the introduction of heavy atom-containing ancillary ligands, such as TPPO or TPAO, along with the careful engineering of the main β-diketone ligand, can increase the luminescence efficiency up to 20-fold by the alteration of the energy migration pathway. It is demonstrated that the combination of two distinct organic ligands leads to the blockage of singlet–triplet intersystem crossing (ISC), alongside electronic energy transfer from β-diketone to Yb³⁺ ions through charge transfer states. The synthesized complexes exhibit quantum yields of 6.5% and 7.0% in the solid state, which places them at the top globally among this class of materials with simple non-deuterated and non-fluorinated ligands. Full article

(This article belongs to the Special Issue Design of Functional Supramolecular Architectures Based on Coordination Compounds)

► Show Figures

Figure 1

33 pages, 1513 KiB

Open AccessArticle

Azirinyl-Substituted Nitrile Oxides: Generation and Use in the Synthesis of Isoxazole Containing Heterocyclic Hybrids

by Alexander S. Dudik, Timur O. Zanakhov, Ekaterina E. Galenko, Mikhail S. Novikov and Alexander F. Khlebnikov

Molecules 2025, 30(13), 2834; https://doi.org/10.3390/molecules30132834 - 2 Jul 2025

Viewed by 597

Abstract

The procedure for the generation of azirinyl-substituted nitrile oxides by the reaction of 2-(diazoacetyl)-2H-azirines with tert-butyl nitrite while preserving the azirine ring has been developed. The [3+2] cycloaddition of azirinyl-substituted nitrile oxides to terminal acetylenes produced azirinyl(isoxazolyl)ketones with various substituents [...] Read more.

The procedure for the generation of azirinyl-substituted nitrile oxides by the reaction of 2-(diazoacetyl)-2H-azirines with tert-butyl nitrite while preserving the azirine ring has been developed. The [3+2] cycloaddition of azirinyl-substituted nitrile oxides to terminal acetylenes produced azirinyl(isoxazolyl)ketones with various substituents in position 3 of azirine and position 5 of isoxazole fragments in a 51–91% yield at room temperature in DCM. DFT calculations and experimental data are consistent with the assumption that the formation of azirinyl-substituted nitrile oxides is accelerated by the acid catalyst. Cycloadducts of nitrile oxides with aryl/hetarylacetylenes and DMAD can be obtained by catalysis with boron trifluoride etherate, which significantly expands the scope of application of the reaction. Expansion of the azirine ring of the prepared cycloadducts allows obtaining a wide range of structurally diverse functionalized isoxazole-containing heterocyclic hybrids. LED light induces isomerization of the azirinecarbonyl moiety of the azirinyl(isoxazolyl)ketones, resulting in the formation of a set of 3,5’-biisoxazoles in a 40–71% yield, while the catalytic reaction of the azirine moiety with 1,3-diketones opens the way to pyrrole- and isoxazole-containing hybrids. 2-(Isoxazole-3-ylcarbonyl)-3-arylazirines were also easily isomerized to 3-(oxazol-5-yl)isoxazoles in methanol in the presence of excess potassium carbonate at room temperature. Full article

► Show Figures

Scheme 1

16 pages, 5250 KiB

Open AccessArticle

Hybrid Additives of 1,3-Diketone Fluid and Nanocopper Particles Applied in Marine Engine Oil

by Yuwen Xu, Yan Yang, Li Zhong, Xingyuan Jing, Xiaoyu Yin, Tao Xia, Jingsi Wang, Tobias Amann and Ke Li

Lubricants 2025, 13(6), 252; https://doi.org/10.3390/lubricants13060252 - 4 Jun 2025

Viewed by 561

Abstract

The lubrication performance of the cylinder liner–piston ring (CLPR) is crucial for the energy efficiency and operating reliability of marine diesel engines. To enhance the boundary lubrication of marine engine oil, a 1,3-diketone fluid HPTD (1-(4-hexylphenyl) tridecane-1,3-dione, HPTD) was introduced as an ash-free [...] Read more.

The lubrication performance of the cylinder liner–piston ring (CLPR) is crucial for the energy efficiency and operating reliability of marine diesel engines. To enhance the boundary lubrication of marine engine oil, a 1,3-diketone fluid HPTD (1-(4-hexylphenyl) tridecane-1,3-dione, HPTD) was introduced as an ash-free friction modifier. Besides that, octadecylamine-functionalized nanocopper particles (ODA-Cu) were also added to the marine oil to improve its anti-wear behavior. Through cylinder-on-disk friction tests, the appropriate contents of HPTD and ODA-Cu were determined, which then formed hybrid additives and modified the engine oil. The tribological performance of the modified oil was analyzed under various normal loads, reciprocating frequencies, and testing temperatures. Based on the synergy of the tribochemical reaction of HPTD and the mending effect of ODA-Cu on the sliding surface, the modified oil not only had lower sulfated ash content but also exhibited superior lubrication performance (i.e., reduced coefficient of friction by 15%, smaller wear track by 43%, and higher maximum non-seizure load by 11%) than the pristine engine oil. The results of this study would be helpful for the design of novel hybrid eco-friendly additives for marine engine oil. Full article

(This article belongs to the Special Issue Marine Tribology)

► Show Figures

Figure 1

15 pages, 6083 KiB

Open AccessArticle

Investigation of 1,3-Diketone and Nano-Copper Additives for Enhancing Boundary Lubrication Performance

by Jingsi Wang, Dezhi Teng, Jiawei Fan, Xi Zhang, Qihang Cui, Ke Li and Pay Jun Liew

J. Mar. Sci. Eng. 2025, 13(5), 912; https://doi.org/10.3390/jmse13050912 - 4 May 2025

Viewed by 582

Abstract

In this work, 1,3-diketone synthesized via the Claisen condensation method and nano-copper particles modified by the Brust–Schiffrin method were added into a commercial marine medium-speed diesel engine cylinder piston oil to evaluate their effects on boundary lubrication performance. Friction and wear tests conducted [...] Read more.

In this work, 1,3-diketone synthesized via the Claisen condensation method and nano-copper particles modified by the Brust–Schiffrin method were added into a commercial marine medium-speed diesel engine cylinder piston oil to evaluate their effects on boundary lubrication performance. Friction and wear tests conducted on CKS-coated piston ring and cast-iron cylinder liner samples demonstrated significant reductions in both friction and wear with the addition of 1,3-diketone and nano-copper particles. Compared to the original oil without additives, the friction force was reduced by up to 16.7%, while the wear of the piston ring and cylinder liner was decreased by up to 21.6% and 15.1% at 150 °C, respectively. A worn surface analysis indicated that the addition of 1,3-diketone and functionalized nano-copper particles influenced the depolymerization and tribo-chemical reactions of the anti-wear additive ZDDP (zinc dialkyldithiophosphate) in the original engine oil. This modification enhanced the oil’s anti-friction and anti-wear properties, offering valuable insights into the development of eco-friendly lubricants for energy-efficient systems. Full article

► Show Figures

Figure 1

17 pages, 5573 KiB

Open AccessArticle

Heteroleptic β-Diketonate Fe³⁺ Complex: Spin-Crossover and Optical Characteristics

by Denis V. Starichenko, Valerya E. Vorobeva, Matvey S. Gruzdev, Ulyana V. Chervonova, Alexander A. Ksenofontov, Aleksey S. Volegov and Ivan V. Yatsyk

Inorganics 2025, 13(5), 134; https://doi.org/10.3390/inorganics13050134 - 25 Apr 2025

Viewed by 612

Abstract

The heteroleptic halogen-substituted Fe³⁺ complex of formula [FeL₂Bipy]Cl, where L is 1-(4-fluoro-phenyl)-3-(4-bromo-phenyl)-propane-1,3-dione and Bipy is 2,2′-bipyridine, was synthesized, and its optic and magnetic properties were studied. Magnetic measurements showed that the complex at high temperatures (T > 75 K) [...] Read more.

The heteroleptic halogen-substituted Fe³⁺ complex of formula [FeL₂Bipy]Cl, where L is 1-(4-fluoro-phenyl)-3-(4-bromo-phenyl)-propane-1,3-dione and Bipy is 2,2′-bipyridine, was synthesized, and its optic and magnetic properties were studied. Magnetic measurements showed that the complex at high temperatures (T > 75 K) is predominantly in the high-spin (HS) state of Fe³⁺ ions (S = 5/2, γ_HS¹ = 93%) with a small admixture of low-spin (LS) state (S = 1/2, γ_LS¹ = 7%). At T* ≈ 46 K, a partial spin-crossover transition (SCO, 5/2↔1/2) occurs. This process is accompanied not only by a change in the magnetic state (γ_HS² = 76%, γ_LS² = 24%), but also by the appearance of AFM interactions (θ_II = −2.3 K) between neighboring Fe³⁺ ions. A theoretical model was proposed to describe magnetic susceptibility, χ(T). As a result of the analysis of the ground spin state M(H) at 2.0 K, it was established that the majority of the LS states, as well as part of the HS states of Fe³⁺ ions (γ_HS ~ 53%), do not participate in exchange interactions. EPR studies confirmed the presence of HS and LS Fe³⁺ centers and made it possible to isolate I-type and II-type HS centers, corresponding to strong low-symmetry and weak distorted octahedral fields. SCO was also detected and the temperature dependences of the EPR intensities, I(T), of the HS and LS centers were analyzed. Full article

(This article belongs to the Section Coordination Chemistry)

► Show Figures

Graphical abstract

6 pages, 1256 KiB

Open AccessCommunication

Synthesis and Intramolecular Regioselective Cyclization of 2-Cyano-3,10-dioxo-1,10-seco-1,25-dinorlupan-28-yl Benzoate

by Irina Tolmacheva, Mikhail Nazarov and Victoria Grishko

Molbank 2025, 2025(2), M1990; https://doi.org/10.3390/M1990 - 7 Apr 2025

Viewed by 583

Abstract

The paper describes the synthesis of a new 1,10-seco-triterpenoid with a 2-cyano-3,10-diketone fragment and its further regioselective cyclization under acidic and basic conditions with the formation of 2S-cyanopyran-3-one derivative or A-pentacyclic alkene β-ketonitrile, respectively. Full article

(This article belongs to the Section Natural Product Chemistry)

► Show Figures

Figure 1

34 pages, 10137 KiB

Open AccessReview

Progress in Luminescent Materials Based on Europium(III) Complexes of β-Diketones and Organic Carboxylic Acids

by Qianting Chen, Jie Zhang, Quanfeng Ye, Shanqi Qin, Lingyi Li, Mingyu Teng and Wai-Yeung Wong

Molecules 2025, 30(6), 1342; https://doi.org/10.3390/molecules30061342 - 17 Mar 2025

Cited by 2 | Viewed by 1546

Abstract

Europium(III) β-diketone and organic carboxylic acid complexes are designable, easy to prepare, and easy to modify and have excellent fluorescence properties (narrow emission spectral band, high colour purity, long fluorescence lifetime, high quantum yield, and a spectral emission range covering both the visible [...] Read more.

Europium(III) β-diketone and organic carboxylic acid complexes are designable, easy to prepare, and easy to modify and have excellent fluorescence properties (narrow emission spectral band, high colour purity, long fluorescence lifetime, high quantum yield, and a spectral emission range covering both the visible and near-infrared regions). These complexes play important roles in popular fields such as laser and fibre-optic communications, medical diagnostics, immunoassays, fluorescent lasers, sensors, anticounterfeiting, and organic light-emitting diodes (OLEDs). In the field of light-emitting materials, europium complexes are especially widely used in OLED lamps, especially because of their high-efficiency emission of red (among the three primary colours); accordingly, these complexes can be mixed with blue and green phosphors to obtain high-efficiency white phosphors that can be excited by near-ultraviolet light. This paper reviews the red-light-emitting europium complexes with β-diketone and organic carboxylic acid as ligands that have been studied over the last five years, describes the current problems, and discusses their future application prospects. Full article

(This article belongs to the Special Issue Exclusive Contributions by the Editorial Board Members (EBMs) of the Inorganic Chemistry Section of Molecules 2024)

► Show Figures

Figure 1

21 pages, 3054 KiB

Open AccessArticle

Curcumin Electroanalysis at a Disposable Graphite Electrode

by Mihaela-Carmen Cheregi, Alina Tirsoaga, Cosmina Ion, Emilia-Elena Iorgulescu, Iulia Gabriela David and Hassan Noor

Biosensors 2025, 15(3), 137; https://doi.org/10.3390/bios15030137 - 23 Feb 2025

Viewed by 1152

Abstract

Curcumin (CU, turmeric), a polyphenolic phytochemical that is largely used as a food spice, has benefits for human health, which have led to increased interest in its therapeutic applications and its analysis from different matrices. The two guaiacol moieties of CU are responsible [...] Read more.

Curcumin (CU, turmeric), a polyphenolic phytochemical that is largely used as a food spice, has benefits for human health, which have led to increased interest in its therapeutic applications and its analysis from different matrices. The two guaiacol moieties of CU are responsible for its antioxidant properties and allow for its voltammetric quantification. Cyclic and differential pulse voltammetry (DPV) investigations at a single-use pencil graphite electrode (PGE) emphasized complex pH-dependent electrode processes, involving an equal number of protons and electrons. Theoretical calculations predicted a folded geometry for the β-diketone CU conformers, which interact with the PGE surface, exposing the electroactive moieties of only one aromatic ring. The Gibbs energy variations of the structures involved in CU electro-oxidation and the theoretical electrochemical potential values were calculated. CU’s DPV cathodic peak intensity recorded at an HB-type PGE in 0.05 mol × L⁻¹ H₂SO₄ varied linearly in the range 5.00 × 10⁻⁸–5.00 × 10⁻⁶ mol × L⁻¹ CU. The method’s detection and quantification limits were 2.12 × 10⁻⁸ mol × L⁻¹ and 6.42 × 10⁻⁸ mol × L⁻¹, respectively. The practical applicability of the developed method, successfully tested by CU assessment in dietary supplements, provided a recovery of 99.28 ± 2.04%. Full article

(This article belongs to the Special Issue Applications of Advanced Electrochemical (Bio)sensors in Environment, Food, and Medicine)

► Show Figures

Figure 1

15 pages, 3388 KiB

Open AccessArticle

Synthesis, Photo-Physical Properties, and Electroluminescence Characteristics of Iridium Phosphorescent Materials Based on Different β-Diketonate Ancillary Ligands

by Qiaowen Chang, Ke Zhang, Caixian Yan, Liming Xie, Yuanqiuqiang Yi, Wenming Su and Weiping Liu

Molecules 2025, 30(4), 861; https://doi.org/10.3390/molecules30040861 - 13 Feb 2025

Cited by 1 | Viewed by 719

Abstract

Organic light-emitting diodes (OLEDs) based on phosphorescent materials are among the most promising technologies for displays and lightings. For red-emitting heteroleptic iridium complexes (HICs), vast and major research has been focused on the design and synthesis of cyclometalated ligands, while relatively little attention [...] Read more.

Organic light-emitting diodes (OLEDs) based on phosphorescent materials are among the most promising technologies for displays and lightings. For red-emitting heteroleptic iridium complexes (HICs), vast and major research has been focused on the design and synthesis of cyclometalated ligands, while relatively little attention has been given to ancillary ligands which also play important roles in manipulating the optoelectronic and electroluminescent properties of HICs. Seven deep red-emitting HICs were designed and synthesized by systematically modifying the alkyl groups in β-diketone-type ancillary ligands. These HICs exhibited similar physical and optoelectronic properties, with OLED devices based on these materials achieving consistent emission peaks at 624 nm and CIE coordinates of (0.68, 0.32). Among the synthesized HICs, Ir(dmippiq)₂(dmeacac), featuring 3,7-dimethyl-4,6-nonanedione as the ancillary ligand, demonstrated the best OLED performance, achieving a champion external quantum efficiency (EQE) of 18.26%. This result highlights that engineering the alkyl groups in β-diketone ancillary ligands can significantly enhance device performance. Full article

(This article belongs to the Section Materials Chemistry)

► Show Figures

Graphical abstract

21 pages, 2416 KiB

Open AccessArticle

Preparation and Transformations of Acetophenone-Derived Enamino Ketones, BF₂-β-Ketoiminates, and BF₂-β-Diketonates

by Helena Brodnik, Luka Ciber, Uroš Grošelj, Nejc Petek, Bogdan Štefane and Jurij Svete

Molecules 2025, 30(3), 601; https://doi.org/10.3390/molecules30030601 - 29 Jan 2025

Viewed by 1207

Abstract

A series of differently substituted β-enaminones 2a,b, 4a–i, 8a–d, and 9–13, their BF₂-β-ketoiminate complexes 5a–d, and BF₂-β-diketonate complexes 6a–d were prepared as [...] Read more.

A series of differently substituted β-enaminones 2a,b, 4a–i, 8a–d, and 9–13, their BF₂-β-ketoiminate complexes 5a–d, and BF₂-β-diketonate complexes 6a–d were prepared as model substrates for photochemical transformations. The attempted photochemical transformations of enaminones 2, 4, 8 and BF₂-β-ketoiminate complexes 5 failed. On the other hand, irradiation of mixtures of BF₂-β-diketonate complexes 6a–d and cycloalkanes with UV-A light (365 nm) gave the corresponding De Mayo reaction products 7a–f in 9–30% yields. The photochemical ring-expansion of acetyl tetralone-derived BF₂-complex 6d gave novel diannulated cyclooctane derivatives 7e and 7f, which would be difficult to obtain using conventional cyclization methods. Full article

(This article belongs to the Section Organic Chemistry)

► Show Figures

Graphical abstract

16 pages, 3432 KiB

Open AccessArticle

Chemoselective Transfer Hydrogenation over MgO as the Catalyst: Acetylnaphthalenes, Diacylbenzenes, Acetophenone, Benzaldehyde, and Various Aliphatic Ketones as Hydrogen Acceptors

by Marek Gliński, Olga Dubinin, Klaudia Rostek and Patrycja Waniek

Reactions 2025, 6(1), 4; https://doi.org/10.3390/reactions6010004 - 4 Jan 2025

Cited by 2 | Viewed by 1115

Abstract

Liquid and vapor phase transfer hydrogenation with 2-alkanols as hydrogen donors in the presence of MgO as a catalyst was studied. A series of dicarbonyl compounds as well as the equimolar mixtures of various monocarbonyl compounds were used as hydrogen acceptors in order [...] Read more.

Liquid and vapor phase transfer hydrogenation with 2-alkanols as hydrogen donors in the presence of MgO as a catalyst was studied. A series of dicarbonyl compounds as well as the equimolar mixtures of various monocarbonyl compounds were used as hydrogen acceptors in order to determine the chemoselectivity (ChS) in the reduction of their carbonyl groups. Thus, 1,4-diacetylbenzene was reduced to 1-(4-acetylphenyl)-1-ethanol with 89% ChS and 1,3-diacetyl-4,6-dimethylbenzene with 100% ChS. Mesitylene diacyl derivatives were unreactive in the studied reaction. CTH of an equimolar mixture of benzaldehyde and acetophenone gave benzyl alcohol and 1-PhEtOH with yields of 91 and 3%, respectively (97% ChS). An equimolar mixture of acetophenone and 6-undecanone underwent CTH with yields of the corresponding alcohols of 89 and 2%, respectively, with 98% ChS towards 1-PhEtOH. Significant differences in reactivity in CTH were reported for an equimolar mixture of regioisomeric 1- and 2-acetylnaphthalenes. The yields of the corresponding alcohols were 20 and 68% with a ChS of 77% towards 2-NphCH(OH)Me. In the case of CTH of 3-oxo-2,2-dimethylbutanal and 2,4-bis(spirocyclohexyl)-1,3-cyclobutanedione with 2-propanol, only the solvolysis of the substrates was observed. The products were methyl isopropyl ketone and isopropyl formate for the former diketone and 1-(cyclohexylcarbonyl)-1-(carboisopropoxy)cyclohexane for the latter. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2024)

► Show Figures

Figure 1

15 pages, 1796 KiB

Open AccessArticle

Rh(III)-Catalyzed Double Annulation of 3-Phenyl-1,2,4-oxadiazoles with 2-Diazo-1,3-diketones: Access to Pyran-Fused Isoquinolines

by Enshen Zhang, Mei Sun and Lvlv Gao

Molecules 2025, 30(1), 149; https://doi.org/10.3390/molecules30010149 - 2 Jan 2025

Cited by 1 | Viewed by 988

Abstract

Efficient access to pyranoisoquinoline derivatives via rhodium-catalyzed double C-H functionalization of phenyl oxadiazoles and diazo compounds has been developed. Two C-C bonds and one C-O and C-N bond formation was realized by this tandem reaction, along with the formation of two heterocycles, affording [...] Read more.

Efficient access to pyranoisoquinoline derivatives via rhodium-catalyzed double C-H functionalization of phenyl oxadiazoles and diazo compounds has been developed. Two C-C bonds and one C-O and C-N bond formation was realized by this tandem reaction, along with the formation of two heterocycles, affording diversified pyran-fused isoquinolines in moderate to good yields with broad functional group tolerance under mild reaction conditions. Full article

► Show Figures

Graphical abstract

18 pages, 3162 KiB

Open AccessArticle

Isolated Dipolar ONN Schiff Base Regioisomers: Synthesis, Characterization and Crystallographic Study

by Pablo Castro-Tamay, David Villaman, Jean-René Hamon and Néstor Novoa

Molecules 2024, 29(24), 5863; https://doi.org/10.3390/molecules29245863 - 12 Dec 2024

Viewed by 829

Abstract

Organic compounds with 1,3-diketone or 3-amino enone functional groups are extremely important as they can be converted into a plethora of carbo- or heterocyclic derivatives or can be used as ligands in the formation of metal complexes. Here, we have achieved the preparation [...] Read more.

Organic compounds with 1,3-diketone or 3-amino enone functional groups are extremely important as they can be converted into a plethora of carbo- or heterocyclic derivatives or can be used as ligands in the formation of metal complexes. Here, we have achieved the preparation of a series of non-symmetrical β-ketoenamines (O,N,N proligand) of the type (4-MeOC₆H₄)C(=O)CH=C(R)NH(Q) obtained through the Schiff base condensation of 1,3-diketones (1-anisoylacetone, 1-anisyl-3-(4-cyanophenyl)-1,3-propanedione, and 1-anisyl-3-(4,4,4-trifluorotolyl)-1,3-propanedione) functionalized with electron donor and electron-withdrawing substituents and 8-aminoquinoline (R = CH₃, 4-C₆H₄CN, 4-C₆H₄CF₃; Q = C₉H₇N). Schiff base ketoimines with a pendant quinolyl moiety were isolated as single regioisomers in yields of 22–56% and characterized with FT-IR, ¹H NMR, and UV-visible spectroscopy, as well as single-crystal X-ray crystallography, which allowed for the elucidation of the nature of the isolated regioisomers. The regioselectivity of the condensation of electronically unsymmetrical 1,3-diaryl-1,3-diketones with 8-aminoquinoline was studied by ¹H NMR, providing regioisomer ratios of ~3:1 and ~2:1 in the case of CN and CF₃ substituents, respectively. The electronic effects correlate well with the difference between the Hammett σ⁺ coefficients of the two para substituents on the aryl rings. Full article

(This article belongs to the Special Issue The 160th Anniversary of the Schiff Base Discovery: Obtaining Functional Molecules with Schiff Bases)

► Show Figures

Figure 1

14 pages, 2408 KiB

Open AccessArticle

Synthesis Comparative Electrochemistry and Spectroelectrochemistry of Metallocenyl β-Diketonato Dicarbonyl Complexes of Rhodium(I)—Cytotoxicity of [Rh(FcCOCHCOCF₃)(CO)₂]

by Eleanor Fourie, J. W. (Hans) Niemantsverdriet and Jannie C. Swarts

Inorganics 2024, 12(12), 321; https://doi.org/10.3390/inorganics12120321 - 11 Dec 2024

Cited by 1 | Viewed by 1005

Abstract

The metallocenyl-containing β-diketonato rhodium(I) dicarbonyl complexes of [Rh(FcCOCHCOR)(CO)₂] where R = CF₃, 10; Fc = ferrocenyl = Fe^II(C₅H₅)(C₅H₄), 11; Rc = ruthenocenyl = Ru^II(C₅ [...] Read more.

The metallocenyl-containing β-diketonato rhodium(I) dicarbonyl complexes of [Rh(FcCOCHCOR)(CO)₂] where R = CF₃, 10; Fc = ferrocenyl = Fe^II(C₅H₅)(C₅H₄), 11; Rc = ruthenocenyl = Ru^II(C₅H₅)(C₅H₄), 12; and Oc = osmocenyl = Os^II(C₅H₅)(C₅H₄), 13 were synthesized. Complexes 10–13 were then subjected to an electrochemical study utilizing cyclic voltammetry (CV), square wave voltammetry (SWV), and linear sweep voltammetry (LSV) in the non-coordinating solvent/supporting electrolyte medium CH₂Cl₂/0.1 mol dm⁻³ [N(ⁿBu)₄][B(C₆F₅)₄]. The formal reduction potential for the electrochemical reversible Fc^0/+ couples in 10–13 was identified in the range 0.156 ≤ E^o′ ≤ 0.328 V while the electrochemically irreversible osmocenyl and ruthenocenyl oxidations were observed at peak anodic potentials of E_pa = 0.640 V and E_pa = 0.751 V, respectively. Resolution between the closely overlapping CV-determined Fc^0/+ and Rh^I/II couples was too poor for unambiguous measurement of the Rh^I/II redox potential, but square wave voltammetry allowed estimates of E^o′ (Rh^I/II) in the range 0.156 ≤ E^o′ ≤ 0.398 V. FT-IR spectroelectrochemistry confirmed the one-electron oxidation of Rh^I by the appearance of CO vibrational bands at stretching frequencies, which are associated with rhodium(II) and not rhodium(III). Cytotoxicity tests on 10 (IC₅₀ = 19.2 µM) showed it to be substantially less cytotoxic than the free β-diketone, FcCOCH₂COCF₃, and [Rh(FcCOCHCOCF₃)(cod)]. Full article

► Show Figures

Graphical abstract

Search Results (239)

Further Information

Guidelines

MDPI Initiatives

Follow MDPI

Saved Queries

Search Filter Reset All

Years

Feature Papers

Subjects

Journals

Article Types

Countries / Regions

Search Results (239)

Further Information

Guidelines

MDPI Initiatives

Follow MDPI