Search

The synthesis of Fe(η 5-C 5 H 4 CH 2 OC(O)R) 2 , 1,2-/1,3-/1,4-(FcCH 2 O) 2 -C 6 H 4 and 1,3,5-(FcCH 2 O) 3 -C 6 H 3 is discussed. The solid state structures of five compounds are reported. Electrochemical investigations show reversible Fc/Fc+ redox events. DFT calculations reveal different HOMO-LUMO gaps depending on the aryl substituent pattern. • Synthesis of ferrocenylmethyl aryl esters; electrochemistry shows reversible Fc/Fc+ events. • Molecular solid state structures confirm anti-periplanar orientations of the 1,1′-positioned substituents. • DFT calculations revealed different degrees of HOMO-LUMO gaps depending on the positions of the carboxylic ester substituents on the aryl rings. The reaction of [Fe(η 5-C 5 H 4 CH 2 OH) 2 (1) with 2 equiv of ClC(O)R (2) (a , R = C 6 H 5 ; b , R = 2-CH 3 -C 6 H 4 ; c , R = 3-CH 3 -C 6 H 4 , d , R = 4-CH 3 -C 6 H 4) produced the corresponding ferrocenyl carboxylates [Fe(η 5-C 5 H 4 CH 2 OC(O)R) 2 (3a–d). Treatment of [FcCH 2 OLi] (4 -Li) (Fc = Fe(η 5-C 5 H 5)(η 5-C 5 H 4)) with (ClC(O)) 2 C 6 H 4 (5) (a , 1,2-((ClC(O)) 2 -C 6 H 4 ; b , 1,3-((ClC(O)) 2 -C 6 H 4 ; c , 1,4-((ClC(O)) 2 -C 6 H 4) in a 2:1 M ratio gave (FcCH 2 OC(O)) 2 -C 6 H 4 (6a – c), while with 1,3,5-(ClC(O)) 3 -C 6 H 3 (7) in a 3:1 M ratio produced 1,3,5-(FcCH 2 OC(O)) 3 -C 6 H 3 (8). All compounds were characterized by NMR (1H, 13C{1H}) and IR spectroscopy, ESI-TOF mass spectrometry and elemental analysis. The molecular structures of 3a – d and 6b in the solid state were determined by single crystal X-ray structure analysis, showing anti-periplanar orientations of the 1,1′-positioned substituents at ferrocene (3a – d). In the cyclic voltammograms of 3a – d , 6a – d and 8 reversible electrochemical redox processes (Fc/Fc+) were observed, ranging between 146 and 164 mV for 3a – d , ca. 100 mV for 6a – d and at 113 mV for 8 using [N n Bu 4 [B(C 6 F 5) 4 as the supporting electrolyte. The molecular electronic structure of 3 , 6 and 8 was calculated by DFT methods in order to obtain the HOMO and LUMO absolute and relative energies in addition to electron density and distribution within the molecular arrangements. It was found that different degrees of HOMO-LUMO energy gaps within the series, due to a lowering in the LUMO energy depending on the positions of the carboxylic ester substituents on the aryl rings, are in agreement with the electrochemical results obtained. [ABSTRACT FROM AUTHOR]

Straightforward synthetic methodologies for the preparation of N -(4-R-phenyl)- N' -(4-nitrophenyl)-oxamate Zincate(II)complexes are discussed. The molecular solid state structures of three compounds are reported. Photoluminescence properties of the Zn(II) complexes in solid state were studied by varying electron-donating substituents at the 4′-position of the phenyl ring. [Display omitted] • Synthesis of N -(4-nitrophenyl)- N '-(4- substituted phenyl)- oxamate Zincate(II) complexes. • Compounds 3a − e were crystallographically characterized. • The optical analyses of zinc complexes (3a – e) show strong emission band in the visible region. The electronic effects electron donating and withdrawing groups R on the properties of N -(4-R-phenyl)- N' -(4-nitrophenyl)oxamito zincate(II) complexes was investigated featuring R = Me (a), H (b), F (c), Cl (d) and Br (e). The N -(4-R-phenyl)- N' -(4-nitrophenyl)oxamide ligands 2 were synthesized by reacting ethyl 4-nitrooxanilate with the respective 4-substituted anilines. Subsequent treatment with [ n Bu 4 N]OH and [Zn(OAc) 2 (H 2 O) 2 ] gave the respective zincate complexes [ n Bu 4 N] 2 [Zn(N -(4-nitrophenyl)- N' -(4-substituted phenyl)oxamides) 2 ] (3). Spectroscopic methods were used to describe compounds 2a – e and 3a – e. Single crystal X-ray diffraction analysis confirmed the formation of 3a–c in the solid state. The tetrahedral coordination sphere of the zinc (II) ion features four amide nitrogen donor atoms based on two ethanediamide ligands. The UV–Vis spectra of Complexes 3a – e display a characteristic LLCT (π → π *) band, which was confirmed by TD-DFT calculations. DFT calculations show that the Zn(II) orbitals do not contribute to the HOMO or LUMO, with the latter being primarily found on the two 4-nitrophenyl rings for compounds 3a − e , while the HOMO-1 and HOMO are located on the 4-substituted phenyl rings. Notably, HOMO and LUMO energies and gabs do not differ significantly. Transitions from HOMO to LUMO + 1 are the most important for all ligands. The luminescence properties of solid compounds 3a − e were also investigated at 298 K. Solid state photoluminescence studies reveal that these complexes emit strong yellow-orange luminescence at 450–600 nm with a maximum at about ∼ 500 nm in the cyan region. Furthermore, the thermal stabilities of compounds 3a − e have been investigated. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of four ferrocenyl thiocarboxylate complexes are reported. Thus, treatment of [Fe(η 5 -C 5 H 5 )(η 5 -C 5 H 4 S − )] ( 1 ) with one equivalent of the acid chlorides 2-ClC(O)- c C 4 H 3 X( 2a , X = O; 2b , X = NMe) gave [Fe(η 5 -C 5 H 5 )(η 5 -C 5 H 4 SC(O)-2- c C 4 H 3 X)] ( 3a , X = O; 3b , X = NMe ( b )). When 1,1′-[Fe(η 5 -C 5 H 4 S − ) 2 ] ( 4 ) was reacted with 2-ClC(O)- c C 4 H 3 X in a 1:2 molar ratio then the respective ferrocenyl-1,1'-bis(thiocarboxylates) 1,1′-[Fe(η 5 -C 5 H 4 SC(O)-2- c C 4 H 3 X) 2 ] ( 5a , X = O; 5b , X = NMe ( b )) were produced. The solid state structures of 5a and 5b were determined by X-ray crystal structure analysis. The Crystal structure of 5a indicated the presence of oxygen…oxygen contacts, the inter-oxygen distance is 0.13 Å less than the sum of van der Waals radii. Investigation of Cambridge Structural Data base for 2-substtiuted furan molecules indicated the presence of short O…O contacts in 49 examples. Geometrical analysis of the O…O contacts indicated that the geometrical arrangement of these contacts is very similar to the well-defined C-X…X-C contacts (X = Cl, Br or I). Cyclic voltammetric studies of 3a , b and 5a , b showed reversible events at 158 and 243 mV for 3a , b and at 187 and 284 mV for 5a , b , using [N n Bu 4 ][B(C 6 F 5 ) 4 ] as the supporting electrolyte. It was found that the furyl-functionalized systems resulted in a significant higher Fc/Fc + redox potential ( E 0′ ) as observed for the more electron-rich pyrrolyl derivatives. The Fc/Fc + redox potential ( E 0′ ) for 5a , b is significantly higher than the one for 3a , b , due to the presence of two electron withdrawing thioester groups attached to the ferrocene in 5a , b . [ABSTRACT FROM AUTHOR]

Treatment of two equiv. of [Fe( η 5 -C 5 H 5 )( η 5 -C 5 H 4 SeSiMe 3 )] ( 1 ) with one equiv. of 2,5-(ClC(O)) 2 - c C 4 H 2 X ( 2 ) produced the corresponding ferrocenyl carboselenolates 2,5-[(FcSeC(O)) 2 - c C 4 H 2 X] ( 3 ) ([Fc = Fe( η 5 -C 5 H 5 )( η 5 -C 5 H 4 )]; a , X = O; b , X = NMe; c , X = Se). On the other hand, [Fe( η 5 -C 5 H 4 SiMe 3 ) 2 ] ( 4 ) reacted with 2-ClC(O)- c C 4 H 3 X ( 5 ) in a 1:2 M ratio to give [Fe( η 5 -C 5 H 4 SeC(O)-2- c C 4 H 3 X) 2 ] ( 6) ( a , X = O; b , X = NMe; c , X = Se). Compounds 3a – c and 6a – c have been characterized by elemental analysis, NMR ( 1 H, 13 C{ 1 H}, 77 Se{ 1 H}) and IR spectroscopy. The structures of 3a–c and 6a in the solid state were determined by single crystal X-ray structure analysis. The cyclic voltammetry measurements for 3a – c and 6a – c show reversible electrochemical processes (Fc/Fc + ) between 135 and 170 mV for 3a − c and between 135 and 220 mV for 6a − c using [N n Bu 4 ][B(C 6 F 5 ) 4 ] as the supporting electrolyte. It was found that the furyl- and selenophyl-functionalized systems resulted in a significantly higher Fc/Fc + redox potential ( E 0′ ) as observed for the more electron-rich pyrrolyl derivatives. The Fc/Fc + redox potential ( E 0′ ) for 6a − c is significantly higher than the one for 3a − c , due to the presence of two selenoester moieties attached to the ferrocene in 6a − c . Spectroelectrochemical UV–Vis/NIR studies of 3b reveal that the two Fc/Fc + centers in the mixed-valent species are not electronically intercommunicating via the heterocyclic bridge. [ABSTRACT FROM AUTHOR]