Structural considerations of terdentate ligands: crystal structures of 2,2′ : 6′,2″-terpyridine and 2,6-bis(pyrazol-1-yl)pyridine

Abstract

The crystal structures of the terdentate ligands 2,2' : 6',2"-terpyridine (terpy) and 2,6-bis(pyrazol-l -yl)pyridine (bppy) were determined by single-crystal diffraction studies. The compound terpy crystallizes in the non-centrosymmetric orthorhombic space group P2,2,2, with a = 3.947(1), b = 16.577(7) and c = 17.840(6) A; the structure was refined to R = 0.0745 for all 1087 independent data and R = 0.0470 for those 609 data with F > 60-(F). The compound bppy crystallizes in the centrosymmetric orthorhombic space group Pnma with a = 11.929(3), b = 21.320(3) and c = 3.889(0) A; this structure was refined to R = 0.0409 for all 896 independent data and R = 0.0300 for those 723 reflections with F > 60(F). The structures of the free terpy and bppy ligands were compared directly with the structures of the co-ordinated terpy and bppy ligands in the [RuL(NO,)(PMe,),] [CIO,] complexes (1 = terpy 1 or bppy 2) in order to determine if any ligand structural changes occur upon co-ordination to ruthenium. To act as terdentate ligands, it was observed that both terpy and bppy must adopt the cis,cis ligand configuration a s opposed to the trans,trans configuration found in the solid state and as the equilibrium configuration in solution. Both terpy and bppy distort upon co-ordination t o ruthenium. The greatest distortions for terpy occur primarily at the central pyridine ring. Large distortions were observed for bppy at both in the central pyridine ring and in the terminal pyrazole rings.

2,2':6',2''-Terpyridine(1-methylimidazole-N3)platinum(II) Perchlorate Acetonitrile Solvate

“…The cis N l mPt--N2 and N2--Pt--N3 angles are less than 90 ° [80.5 (3) and 81.3 (3) °, respectively], as is commonly observed in terpyridine complexes (e.g. Bailey, Catalano & Gray, 1993;Yip, Cheng, Cheung & Che, 1993;Jennette, Gill, Sadownick & Lippard, 1976;Aldridge, Stacy & McMillin, 1994 (Bessel et al, 1992). The Pt--N4 distance, 2.021 (6)A, is in good agreement with the expected value of 2.017/~,, which is the average Pt--N(imidazole) distance for 20 cases of Nalkylimidazole-platinum(II) tetracoordinated compounds [sample standard deviation 0.014A (Orpen et al, 1992)].…”

Experimental Evidence of Reversible Crystalline State Transformation of 2,2':6',2"-Terpyridine: Visualization and Seed Effect

“…Resulting crystals were picked up and were washed several times. Structures of the crystals were confirmed as orthorhombic form by comparing the measured powder XRD pattern with a theoretical XRD pattern calculated using a crystal structure data [2] [3]. Melting point of the orthorhombic crystals was reported as 359 -361 K [1].…”

“…Mutai et al, reported two crystal structures of 2,2':6',2"-terpyridine (Figure 1, expressed as terpy hereafter) [1]. In Figure 2, two crystal structures of terpy are shown using reported crystallographic data [2] [3]. A remarkable difference between the two crystal structures is their molecular packing motif.…”

3-(2,2′:6′,2′′-Terpyridin-4′-yloxy)propyl toluene-4-sulfonate

“…The first reported 2,2 0 ;6 0 ,2 00 -terpyridine crystal structure was the unsubstituted compound (Bessel et al, 1992). Recently, the structure of the 4 0 -chloro-2,2 0 ;6 0 ,2 00 -terpyridine precursor (1) that was used to synthesize the title compound (3) was reported (Beves et al, 2006).…”