Carving Out Pores in Redox‐Active One‐Dimensional Coordination Polymers

Abstract

Reduction of the insulating one-dimensional coordination polymer [Cu(abpy)PF ] , 1 a(PF ), (abpy=2,2'-azobispyridine) yields the conductive, porous polymer [Cu(abpy)] , 2 a. Pressed pellets of neutral 2 a exhibit a conductivity of 0.093 S cm at room temperature and a Brunauer-Emmett-Teller (BET) surface area of 56 m g . Fine powders of 2 a have a BET surface area of 90 m g . Cyclic voltammetry shows that the reduction of 1 a(PF ) to 2 a is quasi-reversible, indicative of facile charge transfer through the bulk material. The BET surface area of the reduced polymer 2 can be controlled by changing the size of the counteranion X in the cationic [Cu(abpy)X] . Reduction of [Cu(abpy)X] with X=Br (2 b) or BAr (2 c; BAr =tetrakis(3,5-bis(trifluoromethyl)phenyl)), affords [Cu(abpy)] polymers with surface areas of 60 and 200 m g , respectively.

Reactivity of NO2 with Porous and Conductive Copper Azobispyridine Metallopolymers

“…Powders of [Cu­(abpy)] n display a broad absorbance around ∼2500 cm –1 in the mid-infrared region (Figure S10). This absorbance is the low-energy tail of the band we assign as a predominantly ligand-based intervalence charge transfer (IVCT) band. This IVCT band is absent in the IR spectrum of [Cu­(abpy)] n after NO 2 dosing (Figure S10), suggesting that the product no longer possesses radical abpy ligands.…”

“…Metallopolymer [Cu­(abpy)] n , generated from the chemical reduction of [Cu­(abpy)­PF 6 ] n with Cp 2 Co, was used for all NO 2 reactivity studies. Black powders of [Cu­(abpy)] n were dosed with either a mixture of NO 2 (1%) in dry air (99%) or a mixture of NO 2 (2%) in dry N 2 (98%) at room temperature for variable amounts of time.…”

“…To better understand the metallopolymer’s reactivity with NO 2 , we carried out similar studies with (Cu­(azpy) 2 ) (1) (azpy = phenylazo-2-pyridine), a molecular analogue of [Cu­(abpy)] n where one pyridyl ring per Cu center is replaced by a phenyl ring to prevent bridging to another Cu center. Here, the ligand-based mixed valence is formally designated as Cu + (azpy 0.5– ) 2 . Before exposure of Cu­(azpy) 2 to NO 2 , the major ion observed in positive mode exhibited an m / z value of 429, corresponding to Cu­(azpy) 2 + (Figure S4).…”

“…We previously described the electrically conductive and porous copper azobispyridine (abpy) metallopolymers [Cu­(abpy)] n . These metallopolymers exhibit an unusual combination of substantial conductivity (0.18 S·cm –1 at room temperature) and porosity (90 m 2 ·g –1 ).…”

“…These metallopolymers exhibit an unusual combination of substantial conductivity (0.18 S·cm –1 at room temperature) and porosity (90 m 2 ·g –1 ). The conductivity of the neutral polymer, with oxidation states formally assigned as [Cu + (abpy –• )] n , was attributed to its mixed-valence character . The [Cu­(abpy)] n metallopolymer can be reversibly oxidized at −0.8 V vs Ag/AgNO 3 to the insulating (<10 –10 S·cm –1 ) and nonporous cationic metallopolymer, formally assigned as [Cu + (abpy 0 )­X] n (X = monoanion).…”