Synthesis and characterization of three heptaaza manganese(II) macrocyclic Schiff base complexes containing two 2-pyridylmethyl pendant arms

Abstract

Three new Mn(II) bis(pendant arm)-macrocyclic Schiff base complexes, [MnL n ] 2? (n = 1, 2, 3), have been prepared via cyclocondensation of 2,6-diacetylpyridine with three different branched hexadentate amines (3,6-bis(2-pyridylmethyl)-3,6-diazaoctane-1,8-diamine (1), 3,7-bis(2-pyridylmethyl)-3,7-diazanonane-1,9-diamine (2) and 3,8-bis(2-pyridylmethyl)-3,8-diazadecane-1,10-diamine (3)) in the presence of MnCl 2 in methanol. The ligands, L, are 15-, 16-and 17-membered pentaaza macrocycles having two 2-pyridylmethyl pendant arms [L 1 ; 2,13-dimethyl-6,9-bis(2-pyridylmethyl)-3, 6,9,12,18-pentaazabicyclo[12.3.

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

“…The characteristic bands of the coordinated L were present in the IR spectra of all the complexes, that is, medium bands at ∼2900 cm −1 (stretching CH 2 vibrations), a medium doublet at 1600 and 1580 cm −1 , and medium bands at ∼1470 cm −1 (wagging vibrations of the pyridine ring). 19,52,53 In addition, the spectra of all the complexes exhibit a very strong and broad band at ∼1070 cm −1 assignable to the stretching vibrations of the (ClO 4 ) − anions.…”

“…The disubstituted cyclam (tpy 2 -C, cyclam = 1,4,8,11-tetraazacyclotetradecane) was studied in six-coordinated complexes with first-row transition metals Fe­(II), Ni­(II), or Cu­(II), and [Fe­(tpy 2 -C)]­(BF 4 ) 2 ·H 2 O with a distorted octahedral geometry showed SCO behavior with the spin transition temperature of 150 K . Extended pentaaza macrocycles with two 2-pyridylmethyl pendant arms ( L1 – L5 ) were studied only in Mn­(II) complexes. , Seven-coordinate central atoms were confirmed by X-ray analysis in [Mn­( L1 )]­(ClO 4 ) 2 ·CH 3 CN, and [Mn­( L4 )]­(ClO 4 ) 2 ·H 2 O only, in which the corresponding pentaaza macrocycle was coordinated in an equatorial plane and two nitrogen atoms from pyridine pendant arms in apical positions. 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 ,, and recently reviewed. , 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. , 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 .…”

A new nano‐sized mononuclear Cu (II) complex with N,N‐donor Schiff base ligands: sonochemical synthesis, characterization, molecular modeling and biological activity

“…Furthermore, the IR spectra of compounds exhibited a new band at 399 cm −1 which can be belonged to ν (Cu–N) stretching vibration . The peaks detected in 1570 and 1569 cm −1 regions are corresponded to the C=C in the maleonitrile and pyridine …”