Heteropolynuclear Pt(II)–M(I) Clusters with a C^∧N^∧C Biscyclometalated Ligand

Abstract

The mononuclear complex [(EtO 2 C-C^N^C)Pt(dmpyz)] (1) (dmpyz = 2,5-dimethylpyrazine) has been synthesised by reaction of [(EtO 2 C-C^N^C)Pt(dmso)] (A) with dmpyz in 1:1 molar ratio in dichloromethane. Complex 1 is the precursor for preparing the homodinuclear complex [{(EtO 2 C-C^N^C)Pt} 2 (-dmpyz)] (2) and the heterotrinuclear clusters [{(EtO 2 C-C^N^C)Pt(dmpyz)} 2 M]X (M= Cu, X= PF 6 (3); M= Ag, X= BF 4 (4)). Compounds 1, 2 and 4 were studied by X-ray diffraction methods. In the crystal packing of 1 and 2, the molecules display short intermolecular ••• contacts, which control the solid state emissive behavior. X-ray study on 4 shows two [Pt 2 Ag] sandwich-type clusters in the asymmetric unit, both with the two square-planar "(R-CNC)Pt(dmpyz)" moieties stabilized by two Pt→Ag donoracceptor bonds as well as by  1-and  2-Ag-C interactions. Intramolecular - contacts were found between the pyridine rings of the CNC ligands within the same Pt 2 Ag cluster. 1 H and 195 Pt NMR studies confirm that the Pt 2 M cluster is also retained in solution at room temperature. 195 Pt NMR spectra of 3 and 4 show signals shifted significantly downfield when comparing to that for the monomer (1), which is attributed to presence of Pt-M dative bonds. At lower temperatures (T = 193 K), the copper derivative definitely falls apart, whereas the silver one still holds up unbroken. In solid state at 77 K, compounds 1-4 give red emissions arising from 3  excited states due to the intra-or intermolecular - contacts observed in the crystal structures. As expected, in glassy solutions (77 K), compound 3 displays analogous emissions to those from the starting material (1). Complexes 1 and 2 show structured emission bands which are particularly sensitive to the ex (HE and LE). In contrast, 4 displays an unstructured emission at 680 nm with a shoulder at 556 nm, both are not dependent on the ex. DFT and TDDFT computational studies have been performed on 1 and 2 which support the conclusions drawn from the photophysical studies.

Neutral benzoquinolate cyclometalated platinum(II) complexes as precursors in the preparation of luminescent Pt–Ag complexes

“…The pentafluorophenyl ligand is in a trans position with respect to the nitrogen atom of the bzq ligand. As previously observed in other platinum(II) complexes containing the bzq ligand [13,17,27,30,47,59] or other cyclometalated planar ligands [28,29,60]. The complexes establish a supramolecular arrangement through pÁ Á Áp interactions of the bzq aromatic ring system of different moieties that stack in a parallel fashion, forming an infinite array with interplanar distances of ca.…”

“…Ag bonds have been prepared using anionic Pt(II) precursors, supposedly because of the additional electron density carried by the platinum center [49], some results have been obtained using neutral Pt(II) complexes [28,30,47]. Thus, we have examined the reactions of complexes 1-3 toward the silver salt AgClO 4 with the aim of achieving heterometallic Pt ?…”

“…Metal-metal bonds can act as a link between different subassemblies, making them a valuable tool in molecular or crystal engineering, and giving rise to a variety of structures, from simple linear bimetallic compounds to infinite one-dimensional chains [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. Furthermore, some of these complexes show interesting photophysical and photochemical properties [1][2][3][4][5]7,8,11,17,27,[29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48], which in some cases have been exclusively attributed to the presence...…”

“…M bonds [5,[12][13][14][15][16][17]21,22,26,[28][29][30]46,[49][50][51][52][53][54][55][56][57] the acidic M center being Cu(I), Ag(I), Au(I), Cd(II), Hg(II), Tl(I), Sn(II) and Pb(II). In the course of our recent research, we have studied the use of strong ligand field cyclometalated C^N ligands, such as 7,8-benzoquinolinate (bzq), in the coordination sphere of the Pt precursor [13,14,27,47].…”

Attachment of Luminescent Neutral “Pt(pq)(C≡CtBu)” Units to Di and Tri N-Donor Connecting Ligands: Solution Behavior and Photophysical Properties

“…The combination of the luminescent Pt(II) units in the corners with luminophore N-groups that can act as linkers can be exploited in highly emissive metallacycles [48]. Comparatively, platinum binuclear derivatives bridged by dinitrogen donor ligands are less represented [49][50][51][52][53][54][55][56], and particularly those with cycloplatinated fragments are scarce [49][50][51][52][53].…”