TY - JOUR
T1 - Syntheses and spectroscopic, structural, electrochemical, spectroelectrochemical, and theoretical studies of osmium(II) mono- and bis-alkynyl complexes
AU - West, Patrick J.
AU - Cifuentes, Marie P.
AU - Schwich, Torsten
AU - Randles, Michael D.
AU - Morrall, Joseph P.
AU - Kulasekera, Erandi
AU - Petrie, Simon
AU - Stranger, Robert
AU - Humphrey, Mark G.
PY - 2012/10/15
Y1 - 2012/10/15
N2 - The syntheses of trans-[Os(C≡C-4-C 6H 4X)Cl(dppe) 2] [X = Br (3), I (4)], trans-[Os(C≡C-4-C 6H 4X)(NH 3)(dppe) 2](PF 6) [X = H (5(PF 6)), I (6(PF 6))], and trans-[Os(C≡C-4-C 6H 4X)(C≡C-4-C 6H 4Y)(dppe) 2] [X = Y = H (7), X = I, Y = C≡CSiPr i 3 (8)] are reported, together with improved syntheses of cis-[OsCl 2(dppe) 2] (cis-1), trans-[Os(C≡CPh)Cl(dppe) 2] (2), and trans-[Ru(C≡C-4-C 6H 4I) (NH 3)(dppe) 2](PF 6) (9(PF 6)) (the last-mentioned direct from trans-[Ru(C≡C-4-C 6H 4I)Cl(dppe) 2]), and single-crystal X-ray structural studies of 2-4, 5(PF 6), 6(PF 6), and 7. Ammine complexes 5(PF 6)/6(PF 6) are shown to afford a facile route to both symmetrical (7) and unsymmetrical (8) osmium bis(alkynyl) complexes. A combination of cyclic voltammetry, UV-vis-NIR spectroelectrochemistry, and time-dependent density functional theory (TD-DFT) has permitted identification and assignment of the intense transitions in both the resting state and the oxidized forms of these complexes. Cyclic voltammetric data show fully reversible oxidation processes at 0.32-0.42 V (3, 4, 7, 8) (with respect to ferrocene/ferrocenium 0.56 V), assigned to the (formal) Os II/III couple. The osmium(III) complex (di)cations 5 2+ and 7 + were obtained by in situ oxidation of 5 + and 7 using an optically transparent thin-layer electrochemical (OTTLE) cell. The UV-vis-NIR optical spectra of 5 2+ and 7 + reveal low-energy bands in the near IR region, in contrast to 5 + and 7 which are optically transparent at frequencies below 22 000 cm -1. TD-DFT calculations on trans-1, 2, 5 +, and 7 and their oxidized forms suggest that the lowest-energy transitions are chloro-to-metal charge transfer (trans-1), chloro-to- phenylethynyl charge transfer (2), and metal-to-phenylethynyl charge transfer (5 +, 7) in the resting state and chloro-to-metal charge transfer (trans-1 +), phosphorus-to-metal charge transfer (5 2+), alkynyl-to-metal charge transfer (7 +), or phenylalkynyl-centered π → π* (2 +) following oxidation. The presence of intense CT bands in the resting states and oxidized states and their significantly different nature across the two states, coupled to their strong charge displacement suggest that these species have considerable potential as electrochemically switchable nonlinear optical materials, while the facile unsymmetrical bis(alkynyl)osmium(II) construction suggests potential in construction of multistate heterometallic modular assemblies.
AB - The syntheses of trans-[Os(C≡C-4-C 6H 4X)Cl(dppe) 2] [X = Br (3), I (4)], trans-[Os(C≡C-4-C 6H 4X)(NH 3)(dppe) 2](PF 6) [X = H (5(PF 6)), I (6(PF 6))], and trans-[Os(C≡C-4-C 6H 4X)(C≡C-4-C 6H 4Y)(dppe) 2] [X = Y = H (7), X = I, Y = C≡CSiPr i 3 (8)] are reported, together with improved syntheses of cis-[OsCl 2(dppe) 2] (cis-1), trans-[Os(C≡CPh)Cl(dppe) 2] (2), and trans-[Ru(C≡C-4-C 6H 4I) (NH 3)(dppe) 2](PF 6) (9(PF 6)) (the last-mentioned direct from trans-[Ru(C≡C-4-C 6H 4I)Cl(dppe) 2]), and single-crystal X-ray structural studies of 2-4, 5(PF 6), 6(PF 6), and 7. Ammine complexes 5(PF 6)/6(PF 6) are shown to afford a facile route to both symmetrical (7) and unsymmetrical (8) osmium bis(alkynyl) complexes. A combination of cyclic voltammetry, UV-vis-NIR spectroelectrochemistry, and time-dependent density functional theory (TD-DFT) has permitted identification and assignment of the intense transitions in both the resting state and the oxidized forms of these complexes. Cyclic voltammetric data show fully reversible oxidation processes at 0.32-0.42 V (3, 4, 7, 8) (with respect to ferrocene/ferrocenium 0.56 V), assigned to the (formal) Os II/III couple. The osmium(III) complex (di)cations 5 2+ and 7 + were obtained by in situ oxidation of 5 + and 7 using an optically transparent thin-layer electrochemical (OTTLE) cell. The UV-vis-NIR optical spectra of 5 2+ and 7 + reveal low-energy bands in the near IR region, in contrast to 5 + and 7 which are optically transparent at frequencies below 22 000 cm -1. TD-DFT calculations on trans-1, 2, 5 +, and 7 and their oxidized forms suggest that the lowest-energy transitions are chloro-to-metal charge transfer (trans-1), chloro-to- phenylethynyl charge transfer (2), and metal-to-phenylethynyl charge transfer (5 +, 7) in the resting state and chloro-to-metal charge transfer (trans-1 +), phosphorus-to-metal charge transfer (5 2+), alkynyl-to-metal charge transfer (7 +), or phenylalkynyl-centered π → π* (2 +) following oxidation. The presence of intense CT bands in the resting states and oxidized states and their significantly different nature across the two states, coupled to their strong charge displacement suggest that these species have considerable potential as electrochemically switchable nonlinear optical materials, while the facile unsymmetrical bis(alkynyl)osmium(II) construction suggests potential in construction of multistate heterometallic modular assemblies.
UR - http://www.scopus.com/inward/record.url?scp=84867507468&partnerID=8YFLogxK
U2 - 10.1021/ic202542c
DO - 10.1021/ic202542c
M3 - Article
SN - 0020-1669
VL - 51
SP - 10495
EP - 10502
JO - Inorganic Chemistry
JF - Inorganic Chemistry
IS - 20
ER -