Structure-Property Relationships of Inorganic-Organic Hybrid Semiconducting Se-Fe-Cu-CO Polymers

A novel family of inorganic-organic-hybrid Se-Fe-3(CO)(9)-dipyridyl two- and one-dimensional Cu polymers was synthesized via the three-component liquid-assisted grinding (LAG) of [Cu(MeCN)(4)](+), inorganic cluster [SeFe3(CO)(9)](2-) (I), and rigid conjugated dipyridyls 4,4'-dipyridyl (dpy) and 1,2-bis(4-pyridyl)ethylene (bpee) or flexible conjugation-interrupted dipyridyls 1,2-bis(4-pyridyl)ethane (bpea) and 1,3-bis(4-pyridyl)propane (bpp). They included a cluster-linked 2D polymer, [(mu(4)-Se)Fe-3(CO)(9)Cu-2(MeCN)(dpy)(1.5)](n) (1-dpy-2D), a cluster-pendant 1D chain, [(mu(3)-Se)Fe-3(CO)(9)Cu-2(dpy)(3)](n) (1-dpy-1D), cluster- blocked 1D polymers, [(mu(3)-Se)Fe-3(CO)(9)Cu-2(L)](n) (1-L-1D, L = bpee, bpea), and a cluster-linked 2D polymer, [(mu(4)-Se)-Fe-3 (CO)(9)Cu-2(bpp)(2)], (1-bpp-2D). The reversible dimensionality transformations of these three types of polymers accompanied by the change in coordination modes of 1 were achieved by the LAG addition of 1/[Cu(MeCN)(4)](+) or dipyridyl ligands. These polymers were found to possess tunable low-energy gaps (1.49-1.72 eV) that increased in the order regarding their structural features: cluster-linked 1-dpy-2D and 1-bpp-2D, cluster-blocked 1-bpea-1D and 1-bpee-ID, and cluster-pendant 1-dpy-1D and [(mu(3)-Se)Fe-3(CO)(9)Cu-2(L)(2.5)](n) (L = bpee, 1-bpee-2D; bpea, 1-bpea-2D), indicative of the importance of the participation of cluster 1. The measured electrical conductivities of 1-bpp-2D, 1-bpea-1D, and 1-dpy-1D were 3.13 x 10(-7), 2.92 x 10(-7), and 2.30 x 10(-7) S.cm(-1), respectively, which were parallel for the trend in their energy gaps, revealing semiconducting behaviors, supported by XPS, XANES, and DFT calculations. The surprising semiconductivity of the conjugation-interrupted bpp-linked 1-bpp-2D was mainly ascribed to electron transport via C-H center dot center dot center dot O(carbonyl) hydrogen bonds and aromatic C-H center dot center dot center dot pi contacts within its closely packed 2D layers. Water-/light-stable polymers 1-bpp-2D, 1-bpea-2D, and 1-dpy-1D were also demonstrated to exhibit excellent pseudo-firstorder photodegradation toward nitroaromatics and organic dyes, where cluster-linked polymer 1-bpp-2D performed the best, as predicted by its structural features and narrow energy gap.