Inorganic-organic hybrid Cu-dipyridyl semiconducting polymers based on the redox-active cluster [SFe(CO)]: filling the gap in iron carbonyl chalcogenide polymers

The construction of sulfur-incorporated cluster-based coordination polymers was limited and underexplored due to the lack of efficient synthetic routes. Herein, we report facile mechanochemical ways toward a new series of SFe 3 (CO) 9 -based dipyridyl-Cu polymers by three-component reactions of [Et 4 N] 2 [SFe 3 (CO) 9 ] ([Et 4 N] 2 [ 1 ]) and [Cu(MeCN) 4 ][BF 4 ] with conjugated or conjugation-interrupted dipyridyl ligands, 1,2-bis(4-pyridyl)ethylene (bpee), 1,2-bis(4-pyridyl)ethane (bpea), 4,4′-dipyridyl (dpy), or 1,3-bis(4-pyridyl)propane (bpp), respectively. X-ray analysis showed that bpee-containing 2D polymers demonstrated unique SFe 3 (CO) 9 cluster-armed and cluster-one-armed coordination modes via the hypervalent μ 5 -S atom. These S-Fe-Cu polymers could undergo flexible structural transformations with the change of cluster bonding modes by grinding with stoichiometric amounts of dipyridyls or 1 /[Cu(MeCN) 4 ] + . They exhibited semiconducting behaviors with low energy gaps of 1.55-1.79 eV and good electrical conductivities of 3.26 × 10 −8 -1.48 × 10 −6 S cm −1 , tuned by the SFe 3 (CO) 9 cluster bonding modes accompanied by secondary interactions in the solid state. The electron transport efficiency of these polymers was further elucidated by solid-state packing, X-ray photoelectron spectroscopy (XPS), X-ray absorption near-edge spectroscopy (XANES), density of states (DOS), and crystal orbital Hamilton population (COHP) analysis. Finally, the solid-state electrochemistry of these polymers demonstrated redox-active behaviors with cathodically-shifted patterns compared to that of [Et 4 N] 2 [ 1 ], showing that their efficient electron communication was effectively enhanced by introducing 1 and dipyridyls as hybrid ligands into Cu + -containing networks. SFe 3 (CO) 9 -based Cu-dipyridyl polymers were synthesized by LAG, where their structures/bonding modes/transformations, semiconducting and redox-active behaviors, and electron transport were demonstrated.