Tuning the Magnetic Moment of [Ru₂(DPhF)₃(O₂CMe)L]⁺ Complexes (DPhF=N,N′‐Diphenylformamidinate): A Theoretical Explanation of the Axial Ligand Influence

Abstract

The magnetic behaviour of the compounds containing the [Ru(2)(DPhF)(3)(O(2)CMe)](+) ion (DPhF(-)=N,N'-diphenylformamidinate) shows a strong dependence on the nature of the ligand bonded to the axial position. The new complexes [Ru(2)(DPhF)(3)(O(2)CMe)(OPMe(3))][BF(4)]0.5 CH(2)Cl(2) (1 0.5 CH(2)Cl(2)) and [Ru(2)(DPhF)(3)(O(2)CMe)(4-pic)][BF(4)] (2) (4-pic=4-methylpyridine) clearly display this influence. Complex 1.0.5 CH(2)Cl(2) shows a magnetic moment corresponding to a S=3/2 system affected by the common zero-field splitting (ZFS) and a weak antiferromagnetic interaction, whereas complex 2 displays an intermediate behaviour between S=3/2 and S=1/2 systems. The experimental data of complex 1 are fitted with a model that considers the ZFS effect using the Hamiltonian H(D)=S.D.S. The weak antiferromagnetic coupling is introduced as a perturbation, using the molecular field approximation. DFT calculations demonstrate that, in the [Ru(2)(O(2)CMe)(DPhF)(3)(L)](+) complexes, the energy level of the metal-metal molecular orbitals is strongly dependent on the nature of the axial ligand (L). This study reveals that the increase in the pi-acceptor character of L leads to a greater split between the pi* and delta* HOMO orbitals. The influence of the axial ligand in the relative energy between the doublet and quartet states in this type of complexes was also analysed. This study was performed on the new complexes 1.0.5 CH(2)Cl(2) and 2. The previously isolated [Ru(2)(DPhF)(3)(O(2)CMe)(OH(2))][BF(4)].0.5 CH(2)Cl(2) (3.0.5 CH(2)Cl(2)) and [Ru(2)(DPhF)(3)(O(2)CMe)(CO)][BF(4)].CH(2)Cl(2) (4.CH(2)Cl(2)) complexes were also included in this study as representative examples of spin-admixed and low-spin configurations, respectively. The [Ru(2)(DPhF)(3)(O(2)CMe)](+) (5) unit was used as a reference compound. These theoretical studies are in accordance with the different magnetic behaviour experimentally observed.

Synthesis, structures, and properties of lantern-type dinuclear ruthenium(II,III) complexes cis-[Ru2{3,5-(CF3)2-pf}2(O2CMe)2Cl] and [Ru2{3,5-(CF3)2-pf}3(O2CMe)Cl], 3,5-(CF3)2-pf−=N,N′-bis[3,5-bis(trifluoromethyl)phenyl]formamidinate anion

“…The large D values are common for the lantern-type Ru 2 5+ dinuclear complexes. They are in the range of D = 50-100 cm À1 reported for lantern-type Ru 2 5+ complexes [3][4][5][6]10,13,28,30,31,33,34]. The magnetic interaction between dinuclear units is weak (zJ = À0.35 cm À1 for 3) or negligible (zJ = 0 cm À1 for 4).…”

“…, H 2 O, CO, NO, OPMe 3 , and 4-pic (4-methylpyridine); Y 0 = none or H 2 O) [12,13,[26][27][28][29][30][31]. The packing diagram of 4(acetone)ÁC 6 H 14 is given in Fig.…”

“…N,N 0 -Bis(alkylphenyl, alkoxyphenyl or chlorophenyl)formamidinate anions (R m -pf À ) work as bridging ligands with or without carboxylate ions (R 0 CO 2 À ) for ruthenium ions to give lantern-type dinuclear complexes, [Ru 2 (R m -pf)(O 2 CR 0 ) 3 Cl], [Ru 2 (R m -pf) 2 (O 2 CR 0 ) 2 Cl], [Ru 2 (R m -pf) 3 (O 2 CR 0 )Cl], and [Ru 2 (R m -pf) 4 Cl] [3,[7][8][9]. In the cases of [Ru 2 (R m -pf) 2 (O 2 CR 0 ) 2 Cl], their electronic structure were also reported to be r 2 p 4 d 2 (p ⁄ d ⁄ ) 3 , which can be changed when the other axial ligand takes place of the chloride ligand [10][11][12][13]. We have reported on the Xray crystal structures of cis-[Ru 2 (4-Me-pf) 2 (O 2 CMe) 2 Cl] (1) (4-Me-pf À = N,N 0 -bis(4-methylphenyl)formamidinate anion) and trans-[Ru 2 (2,6-Et 2 -pf) 2 (O 2 CMe) 2 Cl(THF)] (2) (2,6-Et 2 -pf À = N,N 0 -bis(2,6-diethylphenyl)formamidinate anion), where cis-(2:2) or trans-(2:2) arrangement with the formamidinate and acetate bridging ligands is dependent on the bulkiness of the introduced alkyl groups on the phenyl rings [14].…”

Pressure-driven high-to-low spin transition in the bimetallic quantum magnet[Ru2(O2CMe)4]3O’Neal1, Liu2, Miller3 et al. 2014Phys. Rev. B15030View full textAdd to dashboardCite

“…On the other hand, the mixed-valence Ru 2 (II/III) complex can undergo a high → low spin transition or exhibit intermediate admixed spin behavior [50][51][52][53][54][55] . This is because the presence of spin-orbit coupling causes the π ⋆ and δ ⋆ orbital energies to be quite close [50][51][52][53][54][55] , a situation that amplifies the effect of small perturbations.…”

“…This is because the presence of spin-orbit coupling causes the π ⋆ and δ ⋆ orbital energies to be quite close [50][51][52][53][54][55] , a situation that amplifies the effect of small perturbations. Consequently, spin-admixed ruthenium compounds occur 52 .…”