Coordination complexes of 15-membered pentadentate aza, oxoaza and thiaaza Schiff base macrocycles “Old Complexes Offer New Attractions”

Late First-Row Transition-Metal Complexes Containing a 2-Pyridylmethyl Pendant-Armed 15-Membered Macrocyclic Ligand. Field-Induced Slow Magnetic Relaxation in a Seven-Coordinate Cobalt(II) Compound

“…Surprisingly, the magnetic properties of latter complexes in solid state were studied only sporadically in contrast to another group of seven-coordinate complexes of structurally related 15-membered macrocycles 15-pydienN 3 O 2 and 15-pydienN 5 , which have been extensively studied since 1960s 21,22,10a and recently reviewed. 23,24 On the one hand, SCO with transition temperature of 159 K associated with one Fe−O bond break was observed in [Fe (15-pydienN 3 O 2 )-(CN) 2 ]·H 2 O together with light-induced electron spin state trapping effect (LIESST) at temperature 135 K. 10a, 25 On the other hand, structurally similar complex [Fe (15-pydienN 5 )-(CN) 2 ]·H 2 O was found only in low-spin state but also with LIESST at temperature 105 K. 26 Transition-metal complexes of these two Schiff-base ligands were previously often coupled into heteronuclear oligomeric of polymeric complexes with different 30 This revived interest in the seven-coordinate Fe(II), Co(II), and Ni(II) complexes of 15-pydienN 3 O 2 , 15-pydienN 5 , and ligands L6−L9 (Figure 1) during the past decade can be attributed to their high magnetic anisotropy, which is prerequisite for their SMM behavior. For Co(II) and Ni(II) complexes of L8 and L9, it has been predicted theoretically 31 and consequently also confirmed practically, 32,33 that the value of magnetic anisotropy, usually expressed as axial zero-field splitting (ZFS) parameter D, can be tuned/increased by σ-donor/π-acceptor properties of ligands in axial positions 34 and/ or by the symmetry of the equatorial plane (more details are described in Discussion−Static magnetic properties).…”

Elaborated studies on nano-sized homo-binuclear Mn(II), Fe(III), Co(II), Ni(II), and Cu(II) complexes derived from N2O2 Schiff base, thermal, molecular modeling, drug-likeness, and spectral

“…The magnetic moment value of [Mn 2 (L)(OAc) 2 ]·C 2 H 5 OH complex (5.6 BM)is also lower than the spin only magnetic moment value (5.8 BM) for highspin d 5 systems. The absorption bands appearing at 25,412, 20,000, and 18,868 cm −1 can be attributed to 6 A 1 → 4 T 2 (D), 6 A 1 → 4 T 2 (G) and 6 A 1 → 4 T 1 transitions, respectively, are conducting to the proposed tetrahedral geometry [41] (Fig. 4).…”

“…This is mainly due to their ease of preparation, good solubility in common solvents, structural diversities, magnetic, spectral, redox, and catalytic properties [3][4][5][6][7][8]. Transition metal complexes contain oxygen and nitrogen donor Schiff base ligands, which can be modified by choosing the appropriate amine precursors and the ring may serve in coordination field [9].…”

Sulfonated Schiff base Sn(IV) complexes as potential anticancer agents

“…Though a large number of Schiff bases of various types [76][77][78][79][80][81][82][83][84] has been reported, sulfonated Schiff bases [70][71][72][73][74][75] are rare and only a few metal complexes have been investigated structurally, and a restricted number were applied in catalysis, mainly in alkane [70,74] or alcohol oxidation [75] or in the nitro-aldol reaction [71]. Moreover, sulfonated Schiff bases display versatile coordination abilities, forming monomers, dimers, tetramers and polymers (both 1D and 2D) including solvatomorphs [70][71][72][73][74][75].…”