KRISTALNA STRUKTURA FEROMAGNETNOG Co(II)–KOMPLEKSA SA TEREFTALATO-LIGANDIMA

Abstract

Dizajn i sinteza koordinacionih polimera sa mostovnim tereftalato-ligandom (tpht) je atraktivna oblast istraživanja zbog razvoja novih kompleksa sa korisnim osobinama [1]. Koordinacioni polimer {[Co(dipya)(tpht)]·H2O}n, 1, (dipya = 2,2’-dipiridilamin) sintetisan je hidrotermalnom metodom (T=433 K, 96 h). Struktura 1 određena je rendgenskom strukturnom analizom, dok su magnetna svojstva ispitana SQUID magnetometrom. Kompleks 1 kristališe u monokliničnoj P21/n prostornoj grupi sa parametrima ćelije: a=9,837(2), b=14,348(3), c=12,300(3) Å, β=96,35(3)° i V=1725,4(6) Å3 . Atomi Co nalaze se u deformisanom kvadratno-piramidalnom okruženju koje čine tri O-atoma i N-atom u ekvatorijalnoj ravni i N-atom u apikalnom položaju. Svaki Co-atom koordiniran je sa dva kristalografski različita tpht liganda, bishelatnim i bis-monodentatnim, dajući cik-cak lance (slika 1). Formiranje trodimenzione strukture postiže se mrežom vodoničnih veza između lanaca i dodatnim C–H···π interakcijama. Magnetna susceptibilnost kompleksa 1 (slika 2) pokorava se Kirijevom 1/T zakonu na temperaturama višim od 60 K, sa konstantnom vrednošću efektivnog magnetnog momenta µeff od 2,0 µB (umetak na slici 2), što ukazuje da je kompleks 1 nisko-spinski [2]. Slabe feromagnetne interakcije između jona Co2+ na rastojanjima 10,936(2) i 10,842(3) Å utvrđene su na osnovu malog ispupčenja na krivoj χ–T na oko 40 K i porasta µeff na istoj temperaturi [2]. Dodatni kristalografski podaci: M = 412,26 g mol–1 , Z = 4, ρx = 1,587 g cm–3 , F(000) = = 844, µ(MoKα) = 1,031 mm–1 . Utačnjavanje sa F2 (252 parametara) dalo je R1 = 0,0374, wR2 = 0,0688, S = 1,043 za sve podatke, i R1 = 0,0296 za 2948 refleksija sa I ≥ 2σ(I).

The design and synthesis of coordination polymers with bridging terephthalato ligand (tpht) is an attractive area of investigation due to the development of new complexes with desirable properties [1]. A coordination polymer of {[Co(dipya)(tpht)]·H2O}n, 1, (dipya = 2,2’-dipyridylamine) has been synthesized by hydrothermal method (T=433 K, 96 h). The structure 1 was determined by single-crystal XRD analysis, while magnetic properties were examined by SQUID magnetometer. The complex 1 crystallizes in the monoclinic P21/n space group with cell parameters: a=9.837(2), b=14.348(3), c=12.300(3) Å, β=96.35(3)° and V=1725.4(6) Å3 . Co atoms are in a distorted squarepyramidal environment comprised of three O atoms and N atom in the equatorial plane and N atom in the apical position. Each Co atom is coordinated by two crystallographycally different tpht ligands, bis-chelate and bis-monodentate, which resulted in the zigzag chains (Figure 1). A three-dimensional framework is achieved by hydrogen bond network between the chains and by additional C–H···π interactions. Magnetic susceptibility of complex 1 (Figure 2) folows the Curie 1/T low for temperatures above 60 K with constant effective magnetic moment µeff of 2.0 µB (inset in Figure 2) indicating low spin complex 1 [2]. The weak ferromagnetic interactions between Co2+ ions at distances of 10.936(2) and 10.842(3) Å were observed from a small bump on the χ–T curve at approximately 40 K and from increase of µeff at the same temperature [2]. Additional crystal data: M = 412.26 g mol–1 , Z = 4, ρx = 1.587 g cm–3 , F(000) = 844, µ(MoKα) = 1.031 mm–1 . The refinement on F2 (252 parameters) yielded R1 = 0.0374, wR2 = 0.0688, S = 1.043 for all data, and R1 = 0.0296 for 2948 reflections with I ≥ 2σ(I).