Luminescent cadmium coordination polymers synthesized from bis(4-pyridylmethyl)piperazine and isophthalic acid derivatives

Abstract Hydrothermal reaction of cadmium nitrate, 5-substituted isophthalic acid derivatives, and the long-spanning bis(4-pyridylmethyl)piperazine (4-bpmp) ligand afforded a series of crystalline coordination polymers whose topologies and mode of interpenetration depend critically on the nature of the 5-position substituent. {[Cd(mip)(4-bpmp)(H 2 O)]·3H 2 O} n ( 1 , mip = 5-methylisophthalate) and {[Cd(nip)(4-bpmp)(H 2 O)]·3H 2 O} n ( 2 , nip = 5-nitroisophthalate) both display (4,4) grid topologies. {[Cd 4 (hip) 4 (H 2 O) 4 (4-bpmpH) 2 ](hip)·15H 2 O} n ( 3 , hip = 5-hydroxyisophthalate) also manifests a (4,4) grid topology, but is based on {Cd 2 O 2 } and {Cd 2 (OCO) 2 } dimeric units. [Cd(meoip)(4-bpmp)] n ( 4 , meoip = 5-methoxyisophthalate) shows a (4,4) grid topology based only on {Cd 2 (OCO) 2 } dimeric units. {[Cd 9 (meoip) 10 (4-bpmpH) 2 (H 2 O)]·2H 2 O} n ( 5 ) displays a complex 3D coordination polymer net comprised of trimer-based [Cd 6 (meoip) 6 ] n layers linked by meoip ligands to trimer-based [Cd 3 (meoip) 3 (H 2 O)(4-bpmpH) 2 ] n layers. {[Cd 2 (aip) 2 (4-bpmpH)(H 2 O) 2 ](NO 3 )·5H 2 O} n ( 6 , aip = 5-aminoisophthalate) shows 3,4-connected slab motifs with (6 3 )(6 6 ) topology. {[Cd 2 (tbuip) 2 (4-bpmp) 3 ]·8H 2 O} n ( 7 , tbuip = 5- tert -butylisophthalate) exhibits 5-connected slabs with 4 8 6 2 topology, that engage in parallel 2D + 2D → 3D interpenetration. {[Cd 3 (btc) 2 (H 2 O) 8 (4-bpmp)]·6H 2 O} n ( 8 , btc = 1,3,5-benzenetricarboxylate) displays 1D [Cd 3 (btc) 2 (H 2 O) 8 ] n ribbons pillared by 4-bpmp ligands into 2D (6,3) hexagonal nets. {[Cd 2 Cl 4 (4-bpmp) 3 (H 2 O) 2 ]·4-bpmp·H 2 O} n ( 9 ), prepared from cadmium chloride, 4-bpmp, and 1,3,5-benzenetricarboxylic acid. This shows 1D neutral {[Cd 2 Cl 4 (4-bpmp) 3 (H 2 O) 2 ] n ladder motifs that interlock and interpenetrate in a 1D + 1D → 3D manner. Luminescent behavior in the cadmium complexes is ascribed to intra-ligand molecular orbital transitions. The new phases were also surveyed for the ability to detect nitrobenzene in ethanol suspension.