Selective uptake and removal of aromatic and heterocyclic compounds by para-dicyanobenzene-linked, EFe₃(CO)₉-incorporated (E = Te, Se), semiconducting Cu chain polymers

The uptake and removal of volatile and toxic organic compounds is an important issue in modern industrial chemistry because these organic pollutants have long-term effects on public health and the global environment. In this work, we successfully synthesized two novel para-dicyanobenzene (p-DCB)-linked, EFe₃(CO)₉-incorporated (E = Te, Se) 1D polymers [EFe₃(CO)₉Cu₂(p-DCB)_1.5]_n (E = Te, 1a; Se, 1b) from liquid-assisted grinding (LAG) of the di-Cu compounds [EFe₃(CO)₉Cu₂(MeCN)₂] with p-DCB. Polymers 1a and 1b had isomorphous structures with single- and double-p-DCB linkers alternatively connected to Cu atoms of EFe₃(CO)₉Cu₂ (E = Te, Se) cores, in which two p-DCB of the double-p-DCB moiety were parallel-displaced with the π···π interaction on their benzene rings. The selective adsorption of C₇−C₁₀-alkyl aromatics, polycyclic aromatics, and heterocyclic compounds by 1a and 1b was accomplished via neat grinding or THF-aided LAG processes. These reactions led to the formation of the guest molecule (G)-intercalated products, i.e., 1a- and 1b-based polymers [EFe₃(CO)₉Cu₂(p-DCB)_1.5·(G)_m]_n [E = Te, 1a·mG; E = Se, 1b·mG; m = 0.5 or 1] and the THF-introduced single-p-DCB-bridged polymer [TeFe₃(CO)₉Cu₂(p-DCB)·(THF)]_n (2a·1THF). These adsorption activities of 1a and 1b were thoroughly evaluated by single-crystal and powder X-ray analysis and TGA and DSC measurement, where some C−H···π, π···π, and C−H···E (E = O, S) interactions between guest molecules and the p-DCB linkers were observed to stabilize polymer chains. The desorption of volatile heterocyclic (THF, furan, thiophene) or alkyl aromatic (toluene, m-xylene, mesitylene, durene) guest molecules to give the parent polymers 1a and 1b could be achieved by vacuum and recrystallization or stepwise LAG process in the Te system. Importantly, these EFe₃(CO)₉Cu₂-incorporated (E = Te, Se) polymers 1a and 1b, as well as their host−guest adducts, exhibited semiconducting behaviors possessing tunable energy gaps (1.36−1.51 eV) with moderate electrical conductivities ((1.21−6.55)×10^–7 S·cm^–1), in which the guest molecules played a crucial role in modulating the electron transport in the solid state.