Two Four‐Coordinate and Seven‐Coordinate Co^II Complexes Based on the Bidentate Ligand 1, 8‐Naphthyridine Showing Slow Magnetic Relaxation Behavior

Abstract

For al ong time, the cobalt(II) complex ([Co(napy) 4 ](ClO 4 ) 2 )( napy = 1, 8-naphthyridine) has been considered as an eight-coordinate complex without any structuralp roof. After careful considerations, two complexes [Co(napy) 2 Cl 2 ] (1)a nd [Co(napy) 4 ](ClO 4 ) 2 (2)b ased on the bidentate ligand napy were synthesized and structurally characterized. X-ray single-crystal structurald eterminations howed that the cobalt(II) center in [Co(napy) 2 Cl 2 ]( 1)i sf our-coordinate with a tetrahedral geometry (T d ), while [Co(napy) 4 ](ClO 4 ) 2 (2)i s seven-coordinate rather than eight-coordinate with a capped trigonal prism geometry (C 2v ). Direct-current (dc) magnetic data revealed that complexes 1 and 2 possess positive zero-field splitting (ZFS) parameters of 11.08 and 25.30 cm À1 ,r espectively,w ith easy-plane magnetic anisotropy.A lternating current(ac) susceptibility measurements revealed that both complexes showeds lowm agnetic relaxation behaviour.T heoretical calculations demonstrated that the presence of easy-plane magnetic anisotropy (D > 0) for complexes 1 and 2 is in agreement with the experimental data. Furthermore, these results pave the way to obtain four-coordinate and seven-coordinate cobalt(II) single-ion magnets (SIMs)b yusing ab identate ligand.[a] Dr.Supporting information and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Gram-Scale Synthesis of 1,8-Naphthyridines in Water: The Friedlander Reaction Revisited

“…The TLC plates (Merck TLC silica gel 60 F254) were detected under UV light (λ = 254 and 354 nm). Nuclear magnetic resonance spectra were recorded on Bruker AV 400 MHz and Jeol ECZR-400 MHz spectrometers (400 for 1 H NMR, 100 MHz for 13 C NMR). The chemical shift values were reported relative to central CDCl 3 resonance at δ = 7.26 ppm for 1 H NMR and δ = 77 ppm for 13 C NMR.…”

“…Nuclear magnetic resonance spectra were recorded on Bruker AV 400 MHz and Jeol ECZR-400 MHz spectrometers (400 for 1 H NMR, 100 MHz for 13 C NMR). The chemical shift values were reported relative to central CDCl 3 resonance at δ = 7.26 ppm for 1 H NMR and δ = 77 ppm for 13 C NMR. Highresolution mass spectra (HRMS) were measured on a Bruker micro TOF-Q II spectrometer.…”

“…R f = 0.55 (10% methanol/ dichloromethane). 1 H NMR (400 MHz, CDCl 3 ) δ 9.01 (d, J = 4.0 Hz, 1H), 8.07 (d, J = 8.0 Hz, 1H), 7.79 (s, 1H), 7.38 (dd, J = 4.0, 4.0 Hz, 1H), 3.78 (s, 2H), 3.33 (t, J = 8.0 Hz, 2H), 2.86 (t, J = 8.0 Hz, 2H), 2.52 (s, 3H); 13 7-Ethyl-6,7,8,9-tetrahydropyrido[2,3-b][1,6]naphthyridine (10j). A mixture of 2-aminonicotinaldehyde (8) (61.6 mg, 0.5 mmol) and 1-ethylpiperidin-4-one (9j) (68 μL, 0.5 mmol) was stirred in H 2 O (1 mL) followed by the addition of ChOH (3 μL, 1 mol %).…”

“…R f = 0.42 (10% methanol/dichloromethane). 1 H NMR (400 MHz, CDCl 3 ) δ 9.0 (dd, J = 2.0, 2.0 Hz, 1H), 8.05 (d, J = 8.0 Hz, 1H), 7.79 (s, 1H), 7.36 (dd, J = 4.0, 4.0 Hz, 1H), 3.82 (s, 2H), 3.31 (t, J = 8.0 Hz, 2H), 2.89 (t, J = 8.0 Hz, 2H), 2.61 (m, 2H), 1.19 (t, J = 8.0 Hz, 3H); 13 C NMR (100 MHz, CDCl 3 ) δ 160.5, 155.0, 152.9, 136. The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsomega.1c02798.…”

“…The medicinal properties of naphthyridines and their derivatives are the major driving forces to synthesize them on a large scale. Among naphthyridines, 1,8-naphthyridines ( 1 , Figure A) and their derivatives are used as drugs for antimicrobial activities (nalidixic acid, 2 ), − HIV inhibitor ( 3 ), antibacterial activities (gemifloxacin, 4 ), , antitumor activity (vosaroxin, 5 ), etc. − The 1,8-naphthyridine derivatives can also act as monodentate, bidentate, or binucleating bridging ligands ( 6 , Figure A). − They also exhibit excellent thermally activated delayed fluorescence (TADF) and high photoluminescence quantum yield ( 7 ), which make them suitable blue organic light-emitting diodes (OLEDs). It is worth mentioning that the extensively substituted 1,8-naphthyridines and less substituted ones are used as probes to monitor the structure and function of enzymes and proteins.…”