A Tail Does Not Always Make a Difference: Assembly of cds Nets from Co(NCS)2 and 1,4-bis(n-Alkyloxy)-2,5-bis(3,2′:6′,3″-terpyridin-4′-yl)benzene Ligands

Abstract

The consistent assembly of a (65.8) cds net is observed in reactions of cobalt(II) thiocyanate with 1,4-bis(n-alkyloxy)-2,5-bis(3,2′:6′,3″-terpyridin-4′-yl)benzene ligands in which the n-alkyloxy substituents are n-propyl (ligand 3), n-butyl (4), n-pentyl (5), n-hexyl (6), n-heptyl (7), and n-octyl (8). Crystals were grown by layering a methanol solution of Co(NCS)2 over a 1,2-dichlorobenzene solution of each ligand. The choice of crystallization solvents is critical in directing the assembly of the cds net. Single-crystal structures of [Co(NCS)2(3)]n.3.5nC6H4Cl2, [Co(NCS)2(4)]n.5.5nC6H4Cl2, [Co(NCS)2(5)]n.4nC6H4Cl2, [Co(NCS)2(6)]n.3.8nC6H4Cl2, [Co(NCS)2(7)]n.3.1nC6H4Cl2, and [Co(NCS)2(8)]n.1.6nC6H4Cl2.2nMeOH (C6H4Cl2 = 1,2-dichlorobenzene) are presented and compared. The n-alkyloxy chains exhibit close to extended conformations and are accommodated in cavities in the lattice without perturbation of the coordination framework.

Trinodal Self‐Penetrating Versus cds 3‐Dimensional Networks Using Bis(3,2’ : 6’,3’’‐terpyridine) Building Blocks: the Solvent Makes the Difference

“…PXRD data for the bulk materials of [Co(NCS) 2 ( 1 )] n ⋅2 n C 6 H 4 Cl 2 and [Co(NCS) 2 ( 3 )] n ⋅2.5 n C 6 H 5 Cl confirm that the single crystal structures are representative of the bulk sample; solvent loss from crystals of [Co 2 (NCS) 4 ( 2 ) 2 ] n ⋅5.5 n CHCl 3 ⋅0.2 n MeOH contributed to the poor match between experimental and predicted powder patterns. The solvent‐dependent, selective assembly of either a cds or trinodal self‐penetrating 3‐dimensional network in reactions of Co(NCS) 2 with 1 , 2 and 3 is consistent with our previous results using different 1,4‐bis(alkyloxy)‐2,5‐bis(3,2’ : 6’,3’’‐terpyridin‐4’‐yl)benzene ligands [24,25] …”

“…Both the cobalt(II) center and bis(3,2’ : 6’,3’’‐tpy) ligand are 4‐connecting nodes, and each is essentially planar leading to the assembly of a 3‐dimensional network with a cds topology ( Figure 6). Thus, the networks in [Co(NCS) 2 ( 1 )] n ⋅2 n C 6 H 4 Cl 2 , [Co(NCS) 2 ( 2 )] n ⋅4 n C 6 H 4 Cl 2 , and [Co(NCS) 2 ( 3 )] n ⋅2.5 n C 6 H 5 Cl follow the pattern established for solvated [Co(NCS) 2 (L)] n containing bis(3,2’ : 6’,3’’‐tpy) ligands with R=propyl, butyl, pentyl, hexyl, heptyl or octyl ( Figure 1) and in which the lattice solvent is also 1,2‐dichlorobenzene [25] . In [Co(NCS) 2 ( 1 )] n ⋅2 n C 6 H 4 Cl 2 , [Co(NCS) 2 ( 2 )] n ⋅4 n C 6 H 4 Cl 2 , and [Co(NCS) 2 ( 3 )] n ⋅2.5 n C 6 H 5 Cl, the disordering of some of the solvent molecules makes detailed discussion of the structural roles of the solvent molecules difficult.…”

“…and in which the lattice solvent is also 1,2dichlorobenzene. [25] In [Co(NCS) 2 ( 1 31.0, 35.5 [b] 46.7 [a] 34.3 [b] [a] For the tpy unit containing N1 N2 N3. [b] Tpy unit containing N4 N5 N6.…”

“…[24] Preliminary data for crystals grown by layering an MeOH solution of Co(NCS) 2 over a CHCl 3 solution of L with R = n-butyl confirmed the assembly of a trinodal self-penetrating network. [25] These observations motivated us to move to more sterically demanding R groups while at the same time using different solvent mixtures for the reactions of Co(NCS) 2 with ligand L. A phenyl unit also has the potential for π-stacking interactions in the solid state, which may influence the assembly process. Our aim was to see if the structural trends that had so far emerged with alkyloxy substituents would be further supported when the ligand was structurally modified.…”

“…Moving from a ditopic 3,2' : 6',3''-tpy unit to a tetratopic bis(3,2' : 6',3''-tpy) domain modifies the role of the ligand from a linker to a 4-connecting node, and we have recently reported a series of 3-dimensional networks directed by a combination of 4connecting bis(3,2' : 6',3''-tpy) ligands (Figure 1), and a 4-connecting cobalt(II) center. [23][24][25] With one exception, [23] two structural motifs for [Co(NCS) 2 (L)] n compounds persist: a cds network and a trinodal self-penetrating net. [24,25] An overview of our previous results suggested that, for the range of R groups studied, the choice of the substituent in 1 was not the deciding factor, but rather the choice of solvents for crystal growth by layering.…”