Dual-Property Supramolecular H-Bonded 15-Crown-5 Ln(III) Chains: Joint Magneto-Luminescence and ab Initio Studies

Abstract

Two complexes comprising 9-coordinate capped square antiprismatic [Ln(NO)(OH)(MeOH)] units [Ln(III) = Dy 6; Tb 7] are reported in which the metal complexes are hydrogen-bonded to 15C5 (15-crown-5) macrocycles to form supramolecular chains, {[Ln(NO)(OH)(MeOH)]·(15C5)}. Alternating current magnetic susceptibility measurements supported by ab initio studies show field-induced SMM (single-molecule magnet) behavior for 6, but rapid relaxation of the magnetization for 7 because of the presence of dominant quantum tunneling processes as evidenced by the presence of a significant calculated tunnel splitting within the ground-state multiplet. Modeling the high-resolution emission spectra for 6 afforded energies of 37 ± 5 and 28 ± 5 cm for the first-excited-state Stark sublevels of the two crystallographically independent Dy1 and Dy2 ions, in excellent agreement with the calculated values of 31 and 21 cm for ΔE derived from ab initio studies.

Seven-Coordinate Tb3+ Complexes with 90% Quantum Yields: High-Performance Examples of Combined Singlet- and Triplet-to-Tb3+ Energy-Transfer Pathways

“…We attribute this behavior to the non-Kramers nature of the Tb 3+ ion, similarly to what was observed for other Tb 3+ SIMs, which activates efficient mixing between states belonging to different sides of the double potential energy well. [93][94][95] The values obtained for the n exponent of the Raman process are 6.9(2) for I and 6.06 (7) for II, in line with the value of 7 expected for a non-Kramers ion, 96 and differing, as expected, from the lower values encountered in a recent study with the Gd 3+ complex V, [Gd(bbpen)Cl]. 97 The α parameter in Eq.…”

Single-chain magnet behavior in a finite linear hexanuclear molecule

“…First, the selection of metal centers and their surrounding ligands permits an optimization of the magnetic behavior of the SCMs by enhancing the magnetic anisotropy of the metal ion and/or the ratio between intra-and interchain magnetic interactions. [17][18][19] Second, a careful tuning of the organic ligands can provide new properties to the magnetic chains such as luminescence, [20][21][22] photomagnetic behavior, [23][24][25] magnetic switching, 14,[26][27][28][29] magneto-electric coupling, 30,31 magnetochiral dichroism, 32 spin helicity, 33 or gelation ability. 34,35 We have explored this second strategy recently using Tb III ions and nitronyl-nitroxide radicals [36][37][38][39][40][41][42][43][44][45][46][47][48] substituted by alkyl chains.…”

Effect of Second-Sphere Interactions on the Magnetic Anisotropy of Lanthanide Single-Molecule Magnets: Electrostatic Interactions and Supramolecular Contacts

“…In this way, 15-crown-5 has been used to afford supramolecular 15-crown-5 Ln III chains (Ln III = Tb and Dy), where the metal complex molecules are not covalently but hydrogen-bonded to the crown ether ones. Magnetic studies show field-induced SMM behavior for the Dy III complex but rapid relaxation of the magnetization for the Tb III one . Besides, benzo-15-crown-5 has been used to synthesize a Ln III -based SMM, by encapsulation of the [Dy­(OH 2 ) 8 ] 3+ cation between three macrocyclic units, which are hydrogen-bonded to the metal.…”