Supramolecular Approach for Enhancing Single‐Molecule Magnet Properties of Terbium(III)‐Phthalocyaninato Double‐Decker Complexes with Crown Moieties

Abstract

A Tb -phthalocyaninato double-decker ([1] ) single-molecule magnet (SMM) having four 15-crown-5 moieties in one of the ligands was synthesized, and its dimerization and magnetic properties were studied in an attempt to utilize the supramolecular aggregation for enhancing the SMM properties. Aggregation of [1] to form [1 K ] in the presence of K ions was studied by using UV/Vis-NIR absorption and NMR spectroscopies. For the magnetic measurements, [1] and [1 K ] were dispersed in poly(methyl methacrylate) (PMMA). UV/Vis-NIR absorption measurements on the PMMA dispersed samples were used to track the formation of [1 K ] . Direct current (DC) magnetic susceptibility measurements revealed that there were ferromagnetic Tb-Tb interactions in [1 K ] , whereas there was no indication of ferromagnetic interactions in [1] . Upon the formation of [1 K ] from [1] and K ions, the temperature at which the magnetic hysteresis occurred increased from 7 to 15 K. In addition, the area of magnetic hysteresis became larger for [1 K ] , meaning that SMM properties of [1 K ] are superior to those of [1] . Alternating current (AC) magnetic measurements were used to confirm this observation. Magnetic relaxation times at 2 K increased 1000-fold upon dimerization of [1] to [1 K ] , demonstrating the effectiveness of using K ions to induce dimer formation for the improvement of the SMM properties.

Fabricating Bis(phthalocyaninato) Terbium SIM into Tetrakis(phthalocyaninato) Terbium SMM with Enhanced Performance through Sodium Coordination

“…Quite lately, two bis(phthalocyaninato) terbium SIM building units were connected together through ether bonds, resulting in a covalently‐linked tetrakis(phthalocyaninato) lanthanide quadruple‐decker SMM . Recently, two bis(phthalocyaninato) terbium SIM building units were linked by four K + ions, resulting in a co‐facial dimeric SMM . As a result, from the rational design and fabrication viewpoint, self‐assembly of the non‐peripherally substituted phthalocyanine‐involved double‐decker SIM building blocks into the pseudo‐quadruple‐decker SMM Na 2 {Tb(Pc)[Pc(α‐OC 4 H 9 ) 8 ]} 2 through the alkaline sodium ion coordination bonding interaction truly opens a new way towards designing and preparing novel tetrapyrrole lanthanide multiple‐decker SMMs.…”

“…[14] Recently,t wo bis(phthalocyaninato)t erbium SIM building units were linked by four K + ions, resultingi naco-facial dimeric SMM. [15] As ar esult,f rom the rational design and fabrication viewpoint, self-assembly of the non-peripherally substituted phthalocyanine-involved double-decker SIM building blocks into the pseudo-quadruple-deckerS MM Na 2 {Tb(Pc)[Pc(a-OC 4 H 9 ) 8 ]} 2 through the alkaline sodium ion coordination bonding interaction truly opens an ew way towards designing and preparing novel tetrapyrrole lanthanide multiple-decker SMMs. Moreover,i ti sn oteworthy that in comparison with that of the previous results, the enhancement of the magnetic properties from SIM to SMM in the present work represents the most significantc ase.…”

Manipulation of the Coordination Geometry along the C4 Rotation Axis in a Dinuclear Tb3+ Triple‐Decker Complex via a Supramolecular Approach

“…Herein we explored the effects of supramolecular assembly on the magnetic properties. From our previous studies, the arrangement of the spins controlled via molecular design of the coordination environment affects the magnetic interactions . Therefore, the coordination geometry significantly affects the spin relaxation phenomena of Ln 3+ ‐phthalocyaninato (Pc 2− ) triple‐decker complexes .…”

“…Therefore, the coordination geometry significantly affects the spin relaxation phenomena of Ln 3+ ‐phthalocyaninato (Pc 2− ) triple‐decker complexes . In addition, Ln 3+ ‐Pc triple‐decker complexes (Ln 2 Pc 3 ) have an important advantage over Ln 3+ ‐ Pc double‐decker complexes (LnPc 2 ) because the magnetic relaxation processes correspond to the Zeeman splitting when two 4f spin systems are present . Depending on the situation, since there are two 4f spin sites, it is possible to observe τ corresponding to each site.…”

Control of the Spin Dynamics of Single‐Molecule Magnets by using a Quasi One‐Dimensional Arrangement

“…[14] Incorporating Ln-radical-Ln type moieties is also effective for introducing strong exchange interactions (J ex ) between Ln ions to suppress QTM. [22] If the QTM probability occurring in one TbPc 2 unit is P QTM , the probability of QTM simultaneously occurring in a TbPc 2 dimer is P QTM 2 , meaning that QTM is effectively suppressed. [5,16,17] In addition, investigating the influence of the direction of the magnetic dipole interactions acting among [TbPc 2 ] 0 SMMs in the bulk solid on the magnetic relaxation behavior is important for controlling the magnetic properties, which depend on the molecular arrangement.…”