Adapting (4,4) Networks through Substituent Effects and Conformationally Flexible 3,2’:6’,3”-Terpyridines

Abstract

Coordination networks formed between Co(NCS)2 and 4’-substituted-[1,1’-biphenyl]-4-yl-3,2’:6’,3”-terpyridines in which the 4’-group is Me (1), H (2), F (3), Cl (4) or Br (5) are reported. [Co(1)2(NCS)2]n.4.5nCHCl3, [Co(2)2(NCS)2]n.4.3nCHCl3, [Co(3)2(NCS)2]n.4nCHCl3, [Co(4)2(NCS)2]n, and [Co(5)2(NCS)2]n.nCHCl3 are 2D-networks directed by 4-connecting cobalt nodes. Changes in the conformation of the 3,2’:6’,3”-tpy unit coupled with the different peripheral substituents lead to three structure types. In [Co(1)2(NCS)2]n.4.5nCHCl3, [Co(2)2(NCS)2]n.4.3nCHCl3, [Co(3)2(NCS)2]n.4nCHCl3, cone-like arrangements of [1,1’-biphenyl]-4-yl units pack through pyridine...arene π-stacking, whereas Cl...π interactions are dominant in the packing in [Co(4)2(NCS)2]n. The introduction of the Br substituent in ligand 5 switches off both face-to-face π-stacking and halogen...π-interactions, and the packing interactions are more subtly controlled. Assemblies with organic linkers 1–3 are structurally similar and the lattice accommodates CHCl3 molecules in distinct cavities; thermogravimetric analysis confirmed that half the solvent in [Co(3)2(NCS)2]n.4nCHCl3 can be reversibly removed.

Does the Central Nitrogen Atom Make a Difference? A Comparison of Non‐Coordinating Pyridine and Benzene Spacers in Multitopic Ligands

“…Detailed thermogravimetric analysis (TGA) reveals reversible solvent loss. [99] In each (4,4) net in Figure 21, the Co atoms lie in a plane, and this arrangement is observed repeatedly in the compounds listed in Table 2. In contrast, the (4,4) net in [Co-(NCS) 2 (39) 2 ] n (Figure 22a, ligand 39 has a peripheral bromo substituent) has a corrugated profile (Figure 22b) and each rhombus exhibits a folded conformation (internal dihedral angle = 124.3°).…”

“…Those with 36 , 37 and 40 (peripheral H, F and Me, respectively) exhibit the cone motifs ( Figure 21 e ); solvent molecules in solvated [Co(NCS) 2 ( 36 ) 2 ] n , [Co(NCS) 2 ( 37 ) 2 ] n , and [Co(NCS) 2 ( 40 ) 2 ] n occupy two different cavities, but neither is associated with the cone‐shaped clefts. Detailed thermogravimetric analysis (TGA) reveals reversible solvent loss [99] . In each (4,4) net in Figure 21, the Co atoms lie in a plane, and this arrangement is observed repeatedly in the compounds listed in Table 2.…”

“…In contrast, the (4,4) net in [Co(NCS) 2 ( 39 ) 2 ] n ( Figure 22 a , ligand 39 has a peripheral bromo substituent) has a corrugated profile ( Figure 22 b ) and each rhombus exhibits a folded conformation (internal dihedral angle=124.3°). The reasons for this are unclear although we noted in the original publication that the introduction of the Br substituent results in a loss of the face‐to‐face π‐stacking and/or halogen…π‐interactions seen in the networks with ligands 36 , 37 , 38 and 40 [99] …”

“…The reasons for this are unclear although we noted in the original publication that the introduction of the Br substituent results in a loss of the face-to-face π-stacking and/or halogen…π-interactions seen in the networks with ligands 36, 37, 38 and 40. [99] Two solvates of [Co(NCS) 2 (65) 2 ] n (see Scheme 17 for 65) have been crystallized. Whilst both structures possess (4,4) nets, the conformation of the 3,2':6',3"tpy domain, the geometry of the rhombus, and the arrangements of the ligands are solvent dependent.…”

To Be or Not to Be a (4,4) Net: Reactions of 4′-{4-(N,N-Diethylaminophenyl)}- and 4′-{4-(N,N-Diphenylaminophenyl)}-3,2′:6′,3″- and 4,2′:6′,4″-Terpyridines with Cobalt(II) Thiocyanate

“…Our recent investigations into the formation of (4,4) nets assembled from 3,2 :6 ,3 -tpy ligands and Co(NCS) 2 illustrated both the conformational flexibility of the 3,2 :6 ,3 -tpy unit (Scheme 1) and the effects of introducing different alkyloxy substituents in the 4 -position of the 3,2 :6 ,3 -tpy ligand [17][18][19]. We also noted the role that different lattice solvents play in assemblies arising from a combination of Co(NCS) 2 and 4 -{4-(naphthalen-1-yl)phenyl}-3,2 :6 ,3 -terpyridine [20].…”