TY - JOUR

T1 - Conclusive Insight into the Coordination Complexes of a Flexible Bis ( β -diketonato ) Ligand and Their Phase-Dependent Structure : A Multi-Technique Approach

AU - Imperato, Manuel

AU - Nicolini, Alessio

AU - Mironova, Olga

AU - Benassi, Enrico

AU - Demitri, Nicola

AU - Gigli, Lara

AU - Mucci, Adele

AU - Cornia, Andrea

PY - 2025/4/24

Y1 - 2025/4/24

N2 - Multichelating ligands with nuclear spin-free donor atoms are of particular interest for creating stable electronic spin qubits based on paramagnetic transition metal ions. We recently focused on the coordinating ability of the bis(β-diketonato) ligand bdhb2−, featuring two “acac” moieties connected through a 1,3-phenylene bridge (H2bdhb = 1,3-bis(3,5-dioxo-1-hexyl)benzene). The two crystalline complexes of bdhb2− so far isolated and structurally characterized, namely [(VO)2(bdhb)2] (1) and [Co2(bdhb)2(py)4] (2), are dimeric and contain bridging bdhb2− ligands; however, they become mononuclear and quasi-macrocyclic in organic solution. To investigate this unique structural isomerism by high-resolution 1H NMR spectroscopy, we have now synthesized a diamagnetic Zn2+ analogue of 1 and 2, namely [Zn2(bdhb)2(py)2] (3). Although both 2 and 3 are dimeric and contain the same ligands, 3 features only one pyridine molecule per metal ion, whose coordination geometry is square pyramidal rather than tetragonally elongated octahedral. The ESI-MS spectra of 3 in THF and CH2Cl2 contain peaks from both monomeric and dimeric species. However, molecular weight determinations by DOSY and conformational studies based on J-coupling analysis and DFT calculations conclusively prove the rearrangement of 3 into quasi-macrocyclic monomers in THF-d8 and CD2Cl2 solution at room temperature.

AB - Multichelating ligands with nuclear spin-free donor atoms are of particular interest for creating stable electronic spin qubits based on paramagnetic transition metal ions. We recently focused on the coordinating ability of the bis(β-diketonato) ligand bdhb2−, featuring two “acac” moieties connected through a 1,3-phenylene bridge (H2bdhb = 1,3-bis(3,5-dioxo-1-hexyl)benzene). The two crystalline complexes of bdhb2− so far isolated and structurally characterized, namely [(VO)2(bdhb)2] (1) and [Co2(bdhb)2(py)4] (2), are dimeric and contain bridging bdhb2− ligands; however, they become mononuclear and quasi-macrocyclic in organic solution. To investigate this unique structural isomerism by high-resolution 1H NMR spectroscopy, we have now synthesized a diamagnetic Zn2+ analogue of 1 and 2, namely [Zn2(bdhb)2(py)2] (3). Although both 2 and 3 are dimeric and contain the same ligands, 3 features only one pyridine molecule per metal ion, whose coordination geometry is square pyramidal rather than tetragonally elongated octahedral. The ESI-MS spectra of 3 in THF and CH2Cl2 contain peaks from both monomeric and dimeric species. However, molecular weight determinations by DOSY and conformational studies based on J-coupling analysis and DFT calculations conclusively prove the rearrangement of 3 into quasi-macrocyclic monomers in THF-d8 and CD2Cl2 solution at room temperature.

UR - https://www.mendeley.com/catalogue/993dbe54-fcbf-3ed1-bfa7-a302e6fae2e6/

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-105005225212&origin=inward&txGid=bd75ac6c6c14aea531076f9b4a5643a0

U2 - 10.1002/chem.202500697

DO - 10.1002/chem.202500697

M3 - Article

VL - 2

SP - 1

EP - 10

JO - Chemistry - A European Journal

JF - Chemistry - A European Journal

SN - 0947-6539

ER -