Aromatic Versus Heteroradialene Character in Extended Thiophloroglucinol Ligands and their Trinuclear Nickel(II) Complexes

Abstract

Extended phloroglucinol ligands and complexes are best described as nonaromatic heteroradialenes. Herein, the electronic structures of extended thiophloroglucinol ligands and their Ni(II) 3 complexes are evaluated by comparison to their phloroglucinol analogs by means of NMR, FTIR, UV/Vis, and structural parameters. To provide a full set of compounds for this comparison of S versus O substitution, a new triplesalen ligand, its Ni(II) 3 complex, and a new thiophloroglucinol were synthesized. (1) H and (15) N NMR chemical shifts and coupling constants prove that the thiophloroglucinol ligands exist as the N-protonated and not the O-protonated tautomer. (13) C and (15) N NMR chemical shifts and structural parameters further demonstrated that the extended thiophloroglucinol ligands must be described with a predominant thione-enamine (heteroradialene) character despite the participation of a CS double bond. In the Ni(II) 3 complexes, this heteroradialene character is reduced but still predominant.

Synthesis of a New Schiff Base‐like Trinucleating Ligand and its Copper, Vanadyl, and Iron Complexes – Influence of the Bridging Ligand on the Magnetic Properties

“…Intermediates between the two possibilities can also be envisioned. This is, for example, the case for the triplesalene and triplesalophene ligands, where the N‐protonated tautomer is observed for the central phloroglucine unit (best described as heteroradialene), while the outer ring is O‐protonated , . In the case of H 6 L , 1 H and 13 C NMR spectroscopy clearly confirm that it exist in the all‐NH form.…”

Rational Improvement of Single‐Molecule Magnets by Enforcing Ferromagnetic Interactions

“…By FT-IR spectroscopy Ac omparison of the FT-IR spectrao fH 6 feld tBu 2 and H 6 talalen tBu 2 (wholes pectra in Figure S1a, relevant sections in Figure 3a) allows to distinguish the aromatic character in H 6 talalen tBu 2 and the heteroradialene character in H 6 feld tBu 2 .The ligand H 6 feld tBu 2 exhibits two strong bands at 1603 and 1551cm À1 [22] corre- sponding to the exocyclic C=Ca nd C=Os tretchingm odes of the heteroradialene,r espectively. [26] The C=Ns tretch of the terminal ketimine unit appearso nly as as houlder around 1629 cm À1 .I nc ontrast, the ligand H 6 talalen tBu 2 exhibits aC =N stretch of the terminal ligands at 1632 cm À1 and ab undle of bands between 1440 cm À1 and 1465 cm À1 .T hese bands are already observed in the spectrum of the secondary amineu sed as salalen-halfunit for the Mannich reaction with phloroglucinol to obtain H 6 talalen tBu 2 .This demonstratesthe absence of significant contributions of the central phloroglucinol especiallyo f any heteroradialene contribution.…”

“…[22] The structural index parameter for aromaticity, HOMA (harmonic oszillator model of aromaticity), which takes the value of 1f or the model aromatic system benzene and 0 for am odel non-aromatic system, [27] is also ag ood indication. [22] The structural index parameter for aromaticity, HOMA (harmonic oszillator model of aromaticity), which takes the value of 1f or the model aromatic system benzene and 0 for am odel non-aromatic system, [27] is also ag ood indication.…”

“…[27] [ [14] lenes, [17,[20][21][22] while the triplesalalen ligand H 6 talalen tBu 2 exhibits ab and at 30 000 cm À1 of lower intensity originating from the three terminal o-iminephenolu nits.A lso the triplesalen-based [(feld tBu 2 )Mn III 3 ] 3 + exhibitsastronger intensity in this region in line with as trongh eteroradialene contribution [22] in comparison to the triplesalalen-based [(talalen tBu 2 )Mn III 3 ] 3 + .T his manifests the successful heteroradialene suppression in the triplesalalen-based complex. [27] [ [14] lenes, [17,[20][21][22] while the triplesalalen ligand H 6 talalen tBu 2 exhibits ab and at 30 000 cm À1 of lower intensity originating from the three terminal o-iminephenolu nits.A lso the triplesalen-based [(feld tBu 2 )Mn III 3 ] 3 + exhibitsastronger intensity in this region in line with as trongh eteroradialene contribution [22] in comparison to the triplesalalen-based [(talalen tBu 2 )Mn III 3 ] 3 + .T his manifests the successful heteroradialene suppression in the triplesalalen-based complex.…”

“…H 6 talalen tBu 2 [24] and H 6 feld tBu 2 [22] were synthesized according to the published procedures. H 6 talalen tBu 2 [24] and H 6 feld tBu 2 [22] were synthesized according to the published procedures.…”