Dinuclear Cu^I and Ag^I Pyrazolates Supported with Tertiary Phosphines: Synthesis, Structures, and Photophysical Properties

Abstract

New dinuclear silver(I) and copper(I) 3,5-bis(trifluoromethyl)pyrazolate compounds were prepared by the reaction of the corresponding trinuclear metal complexes with tertiary phosphines (PPh 3 , PCy 3 ). In the case of copper(I) trinuclear pyrazolate it was shown that the product structure depends on [a] A. N. Nesmeyanov Institute of Organoelement Compounds, 821 the reagent ratio: mono-and dinuclear complexes were obtained. All the dinuclear complexes obtained exhibit light emission in the solid state under UV irradiation. The observed photoluminescence behavior was confirmed by the TD-DFT study. Scheme 1. Possible paths of 11 group metals pyrazolates formation. Scheme 2. Main motifs of copper(II) (a, b, c), copper(I) and silver(I) (c) dinuclear pyrazolates.dine. [12] Such dinuclear macrocycles can be synthesized from polynuclear [MPz] n , [10a,11a] or trinuclear pyrazolates [11b] or from the corresponding metal salts. [2b] Moreover, dinuclear copper pyrazolate complexes with tertiary phosphines were obtained only with pyrazoles containing strong electron withdrawing NO 2 groups.

Dinuclear Silver(I) Nitrate Complexes with Bridging Bisphosphinomethanes: Argentophilicity and Luminescence

“…The T 6 of MLCT nature is the state coupled with the S 1 excitation, having high similarity (s H = 0.91 and s E = 0.90) to the S 0 → T 6 transition energy 4.02 eV (308 nm) ( Figure 6). Similar behavior was observed in the case of dinuclear silver pyrazolates with PCy 3 and PPh 3 ligands [35].…”

“…The T6 of MLCT nature is the state coupled with the S1 excitation, having high similarity (sH = 0.91 and sE = 0.90) to the S0 → T6 transition energy 4.02 eV (308 nm) ( Figure 6). Similar behavior was observed in the case of dinuclear silver pyrazolates with PCy3 and PPh3 ligands [35]. The TD-DFT analysis of [Ag(dppm)]2(Me2Pz H )(NO3)2 (2a) excitations led to nearly the same pattern, except the disappearance of symmetry forbidden states, which led to doubling of the number of corresponding electronic transitions.…”

“…The results of calculations (vide supra) showed that the T1-T8 states were of LC nature within Ph substituents. As we have shown for structurally similar silver pyrazolate/dppm complexes, these states are not emissive due to the intersection of their energy surface with the ground state, which allows effective non-radiative relaxation [35][36][37]. The emission observed at 298 K can be ascribed to the system relaxation from T11- UV-Vis spectrum of compound 2a showed a broad, intense band at 288 nm (ε = 12800 cm −1 M −1 ) with a long tail at ca.…”

“…Based on these, practically the same conclusion can be made as for 2b. The lowest singlet excitation should lead to the high energy triplets T 11 -T 12 that is likely to interconvert to the lower 3 LC states of dppm' Ph substituents, which in turn has a trend to non-emissive relaxation at room temperature [35][36][37], but could be stabilized at 77 K. UV-Vis spectrum of compound 2a showed a broad, intense band at 288 nm (ε = 12800 cm −1 M −1 ) with a long tail at ca. 335 nm, which can be assigned to the charge-transfer (MLCT or LLCT) transitions.…”

A Computational Study of Metallacycles Formed by Pyrazolate Ligands and the Coinage Metals M = Cu(I), Ag(I) and Au(I): (pzM)n for n = 2, 3, 4, 5 and 6. Comparison with Structures Reported in the Cambridge Crystallographic Data Center (CCDC)

“…As far as dimers are concerned, many of these are Cu(II) derivatives and all examples that contain Cu(I) have complex pyrazolates with arms that are able to coordinate the copper or they have supplementary ligands; dimers in which the Cu(I) atoms are "nude", i.e., linked only to the pyrazolate anion, have not been found. Amongst the supplementary ligands are CO (COCZAY [29], COCZOM [29]), C≡N-R (GITJUO [30], HEDFIF [31], JEMCAF [32]), PPh3 (GITKEZ [30], PIRDAY [33], SATKAC [34]), pyridines (IPIGET [35], KUKLOR [36]) and N-heterocyclic carbenes NHCs (NETLUW [37], NETMAD [37]). The central metallacycle can adopt planar or folded conformations, either boat-type or chair-type ( Figure 3), and both of these conformations are common.…”