Measuring Spin⋅⋅⋅Spin Interactions between Heterospins in a Hybrid [2]Rotaxane

Abstract

Use of molecular electron spins as qubits for quantum computing will depend on the ability to produce molecules with weak but measurable interactions between the qubits. Here we demonstrate use of pulsed EPR spectroscopy to measure the interaction between two inequivalent spins in a hybrid rotaxane molecule.

Self-Assembly in Polyoxometalate and Metal Coordination-Based Systems: Synthetic Approaches and Developments

“…There are numerous other interesting metal coordination cages with remarkable structural features and properties [113][114][115][116][117]. Any effort to discuss every available family of clusters, their general features and functionality would have been fruitless and goes beyond the scope of the present article.…”

Hybrid Organic–Inorganic Rotaxanes, Including a Hetero‐Hybrid [3]Rotaxane Featuring Two Distinct Heterometallic Rings and a Molecular Shuttle

“…Spectra of the [2]rotaxane 6 are those of an isolated high spin Fe III ion (S = 5/2) with axial (j D j)and rhombic (E)zero-field splitting parameters of 0.17 and 0.045 cm À1 ,r espectively.T here are some minor spectral changes in the [3]rotaxane 1 that can be modelled as small changes in E. Similarly,spectra of 3 can be modelled as asingle S = 3/2 (D = À0.53, E = 0.03 cm À1 )owing to Cr III .T he larger j D M j and smaller rhombicity (E/D)f or M = Fe compared to Cr in {Ti 7 M}, and also the magnitudes of D and E,a re typical for monometallic {MO 6 }c omplexes,f or example,[ M(diketonates) 3 ]. [18,19] The D Cr value in {Ti 7 Cr} is significantly larger than that in the parent {Cr 7 M} family: [20] this must be af unction of the {Cr(O carboxylate ) 4 (O) 2 }v ersus {Cr(O carboxylate ) 4 (F) 2 }c rystal fields.T he implication is that oxide is acting as ab etter p-donor, resulting in aw eaker crystal field and hence larger ZFS via mixing with excited states,and that this is more important than the greater charge.…”

“…[5] It is also possible to add additional paramagnetic centres such as Cu II ions [6] or organic radicals. [7] While there are several mechanically interlocked molecules featuring metal ions, [8] they remain unusual. Herein we report an ew family of hybrid rotaxanes based on {Ti 7 M III }r ings.…”

“…[10,11] Thesimplest possible route to a [3]rotaxane is to use adiamine where there is along chain between the amine centres and large groups at each the end to act as stoppers.Therefore, we dissolved an oxo-centred triangle of at rivalent metal (Fe III ,G a III ,C r III ,o rM n III )i np ivalic acid in the presence of dibenzyldecane-1,10-diamine [(PhCH 2 NH 2 ) 2 (CH 2 ) 10 A]a nd trimethylacetic anhydride;[ Ti(O i Pr) 4 ]i st hen added. All manipulations were carried out under nitrogen with rigorous exclusion of water.T he oxo-centred triangles were:[ Fe 3 O-(O 2 C t Bu) 6 (H 2 O) 3 ](O 2 C t Bu)· t BuCO 2 H; [12] [Ga 3 O(O 2 C t Bu) 7 -(CH 3 CN)]·0.5 t BuCO 2 H; [9] [Cr 3 O(O 2 C t Bu) 7 (HO 2 C t Bu) 2 ]generated in situ; [13] [Mn 3 O(O 2 CMe) 7 (HO 2 CMe)] n . [14] Theresult is the formation of a [3]rotaxane,{[A][(Ti 7 MO 8 -(O 2 C t Bu) 16 )] 2 }( M = Fe III 1,G a III 2,C r III 3,o rM n III 4) ( Figure 1).…”

“…Thea bility to grow isostructural but different heterometallic rings around similar threads has also allowed us to make ah etero-heterometallic-hybrid [3]rotaxane.U sing A as the thread we can first grow the very stable {Cr 7 Ni}ring [4] around one ammonium group (see the Supporting Information for experimental details), and then grow a{Ti 7 16 ]} 11,w hich has the same structure as compounds 1-4 ( Figure 1). Synthesis of [3]rotaxanes with different rings as components is unusual, and the ability to grow as upramolecule with two heterometallic components is unique.…”