Blue and red shift hydrogen bonds in crystalline cobaltocinium complexes

Abstract

Typical hydrogen-bonded cobaltocinium salts of formula [Cp 2 Co + ][A À ] [with Cp = C 5 H 5 and A = PF 6 ( 1), AsF 6 ( 2), SbF 6 ( 3), I ( 4), I 3 ( 5), Co(CN) 6 ( 6), Co(CO) 4 ( 7), Br 3 ( 8), FeI 4 ( 9) and HCl 2 ( 10)] were studied by means of a combined structural, spectroscopic (IR, Raman, solid-state NMR) and theoretical approach. The solid-state vibrational spectra show blue or red shift hydrogen bond behavior depending on the anionic species, i.e. high-or low-frequency n(CH) shift with respect to the solution value. The crystal structure of the new complex [Cp 2 Co + ][SbF 6 À ], a blue-shifted system, is reported while the [Cp 2 Co + ][I À ] complex, a red-shifted system disordered at room temperature, reveals a novel ordered polymorph at 150 K. The weak interactions (CÁ Á ÁH, HÁ Á ÁH, HÁ Á ÁX, CÁ Á ÁX) between cations and anions were analyzed by means of the Hirshfeld surfaces model, which permits their clear graphic visualization. HS fingerprint plots and normalized contact distances visually describe the difference between blue-and red-shifted complexes. Chemical shift tensors and shielding anisotropy values of the Cp carbon atoms, extracted from 13 C CPMAS solid-state NMR spectra, allow the evaluation of Cp rotational motions which are related to the intermolecular contact extent. Finally, a DFT computational model is able to rationalize all the experimental data. It shows that the prevalence of one between two forces, that is, the attractive polarization of C-H bonds and the repulsive effect of electronic clouds, leads to the blue or red shift phenomenon.

A Sterically Hindered Derivative of 2,1,3‐Benzotelluradiazole: A Way to the First Structurally Characterised Monomeric Tellurium–Nitrogen Radical Anion

“…According to the single‐crystal XRD analysis, the structure of 2⋅ 2 THF (Figure 1) reveals the presence of [CoCp 2 ] + cations, as is clearly seen from comparison of the average Co−C bond length (2.016 Å) with those in the parent cobaltocene (2.096(8) Å), [33, 34] and cobaltocenium salts [CoCp 2 ]SbF 6 (2.032 Å) [35] and [CoCp 2 ]CF 3 SO 3 (2.023 Å) [36] . Thus, the TeL moiety in 2 should be considered to be an anion; however, the addition of an electron does not lead to dramatic changes in the molecular geometry (Supporting Information, Figures S1, S2).…”

Structure, energy, vibrational spectrum, and Bader's analysis of π⋯H hydrogen bonds and H−δ⋯H+δdihydrogen bonds

“…As it is widely known that suitable analysis of vibrational modes is a decisive factor for describing adequately the formation of intermolecular interactions, [549][550][551] our group reported a theoretical study of dihydrogen-bonded complexes formed by BeH 2 Á Á ÁHX with X = F, Cl, CN, and CCH, in which was proposed the investigation not only of their structural and electronic parameters, but also the characterization of their stretch frequencies and red-shift effects. 552,553 According to Caballero and Jalo ´n, 554 the 'electronegative capacity' of H Àd in BeH 2 can be demonstrated by a theoretical analysis of the ternary dihydrogen-bonded complex, BeH 2 Á Á Á2-(HCl). 555 This observation led us to invest in a computational study in order to confirm the capability of HCN and HNC to form this ternary dihydrogen-bonded complex, not only by evaluating the terminal hydride (8) as a proton acceptor in BeH 2 Á Á Á2(HX), but also simultaneously two (9) hydrides in XHÁ Á ÁBeH 2 Á Á ÁHX, in this case X = CN and NC, as illustrated in the Fig.…”

Copper-paracetamol complexes: Promising lead antibacterial drug candidates

“…There was a blue shift when DMSO quenched the absorption of the reaction products at other wavelengths except 260 nm. Absorption within the visible range is directly affected by DMSO and results in a red shift (a shift in frequency towards lower energy or longer wavelength) and a blue shift (shift in the frequency towards a higher energy or a shorter wavelength) (Diana et al, 2012;Miller et al, 2014). It is therefore indicative from the results that, there was a blue shift in the sample 1, sample 2 and yellow extract.…”