A new cyclometalated derivative, (NBu4)[Pt(bzq)(C6Cl5)2] (2) (bzq = 7,8-benzoquinolate), and three novel polymetallic species containing donor−acceptor Pt→Ag bonds, (NBu4)[{Pt(bzq)(C6F5)2}2Ag] (3) and [{Pt(bzq)(C6X5)2}Ag(PPh3)] (X = F (4), Cl (5)), have been synthesized and characterized by X-ray diffraction methods. 3 is prepared by reaction of (NBu4)[Pt(bzq)(C6F5)2] (1) with AgClO4 in 1:1 or 1:0.5 molar ratio, while 4 and 5 are the results of the reaction of the corresponding (NBu4)[Pt(bzq)(C6X5)2] (X = F (1), Cl (2)) precursors with [Ag(OClO3)(PPh3)] in 1:1 molar ratio. 3 has been found to crystallize in two forms:  monoclinic (3a) and triclinic (3b), which differ not only in the conformation of the basic Pt2Ag anion (anti and planar 3a, staggered and nonplanar 3b), but also in the crystal packing (π···π extended structure 3a, and a stacked dimer 3b) and luminescence at 298 K (orange 3a, green 3b). At 77 K, the orange band (568 nm) of 3a, attributed to a ππ* excimeric emission, is not detected, and both polymorphs exhibit identical green emission (3LC/3MLCT). Spectroscopic study of 4 and 5 (UV−vis and luminescence) was also performed to examine the role of the Pt→Ag donor−acceptor bond. The most significant feature is the blue shift observed in the low-energy UV absorption and the appearance of two, close, distinct, structured emissions with short (487 4; 490 nm 5) and long (502 nm 4, 5) lifetime, but only in the solid state at 77 K.

A novel series of anionic mononuclear terdentate dicyclometalated complexes (NBu4)[Pt(CwedgeNwedgeC)X] (HCwedgeNwedgeCH=2,6-diphenylpyridine) containing acetylide (X=C[triple bond]CR, R=tBu, 1; Ph, 2; Tol, 3; (4-OMe)C6H4, 4) or another anionic ligand (X=CN, 5; S-2Py, 6; CH2COCH3, 7) have been synthesized and fully characterized. The solid-state structures of complexes 1 and 4-6 have also been determined by X-ray diffraction studies, showing, in all the cases, the presence of several types of weak hydrogen interactions, leading to the generation of supramolecular 2D (1) or 3D (4-6) architectures. All the complexes (1-7) are intensely luminescent at low temperature (solid and glassy CH2Cl2), exhibiting concentration dependence in the emissions of the glassy CH2Cl2 matrix.

Luminescent mono(pentafluorophenyl) cycloplatinated complexes [Pt(C^N-κC,N)(HC^N-κN)(C6F5)] [HC^N = Hthpy (2-(2-thienyl)pyridine) 2a, Hbt (2-phenylbenzothiazole) 2b, Hpq (2-phenylquinoline) 2c] have been prepared by C–H activation of a HC^N ligand in the corresponding [Pt(HC^N-κN)2(C6F5)2] (1a, 1b, 1c) complexes. Complexes 2 evolve in DMSO solution into solvate complexes and we present here successful routes for the synthesis of [Pt(C^N)(C6F5)(DMSO)] (C^N = thpy 3a, bt 3b). They have been fully characterized (X-ray for 1a, 1c, 2b, 3a and 3b), their electronic absorption and emission properties have been investigated and DFT and TD-DFT calculations for 1a, 1c, 2b and 3a have been carried out. Complexes 3a, 3b and [Pt(ppy)(C6F5)(DMSO)] 4 (Hppy = 2-phenylpyridine) show remarkable stability in a mixed DMSO-cellular medium and their cytotoxicity towards the human lung tumor (A549) and bronchial epithelial non-tumorigenic (NL20) cell lines has been evaluated by MTS assays. Their cellular localization in A549 and NL20 human cells and in mouse embryonic fibroblasts obtained from lungs (LMEFs) has also been investigated by fluorescence microscopy.

A novel series of [PtTl(2)(C[triple chemical bond]CR)(4)](n) (n = 2, R = 4-CH(3)C(6)H(4) (Tol) 1, 1-naphthyl (Np) 2; n = infinity, R = 4-CF(3)C(6)H(4) (Tol(F)) 3) complexes has been synthesized by neutralization reactions between the previously reported [Pt(C[triple chemical bond]CR)(4)](2-) (R = Tol, Tol(F)) or novel (NBu(4))(2)[Pt(C[triple chemical bond]CNp)(4)] platinum precursors and Tl(I) (TlNO(3) or TlPF(6)). The crystal structures of [Pt(2)Tl(4)(C[triple chemical bond]CTol)(8)]4 acetone, 14 acetone, [Pt(2)Tl(4)(C[triple chemical bond]CNp)(8)]3 acetone1/3 H(2)O, 23 acetone 1/3 H(2)O and [[PtTl(2)(C[triple chemical bond]CTol(F))(4)](acetone)S](infinity) (S = acetone 3 a; dioxane 3 b) have been solved by X-ray diffraction studies. Interestingly, whereas in the tolyl (1) and naphthyl (2) derivatives, the thallium centers exhibit a bonding preference for the electron-rich alkyne entities to yield crystal lattices based on sandwich hexanuclear [Pt(2)Tl(4)(C[triple chemical bond]CR)(8)] clusters (with additional Tlacetone (1) or Tlnaphthyl (2) secondary interactions), in the C(6)H(4)CF(3) (Tol(F)) derivatives 3 a and 3 b the basic Pt(II) center forms two unsupported Pt-Tl bonds. As a consequence 3 a and 3 b form an extended columnar structure based on trimetallic slipped PtTl(2)(C[triple chemical bond]CTol(F))(4) units that are connected through secondary Tl(eta(2)-acetylenic) interactions. The luminescent properties of these complexes, which in solution (blue; CH(2)Cl(2) 1,2; acetone 3) are very different to those in solid state (orange), have been studied. Curiously, solid-state emission from 1 is dependent on the presence of acetone (green) and its crystallinity. On the other hand, while a powder sample of 3 is pale yellow and displays blue (457 nm) and orange (611 nm) emissions, the corresponding pellets (KBr, solid) of 3, or the fine powder obtained by grinding, are orange and only exhibit a very intense orange emission (590 nm).

A comparison of the solid structures of three novel trinuclear sandwich Pt 2 Pb systems (NBu 4 ) 2 [{Pt(C≡CTol) 4 } 2 Pb(OH 2 ) 2 ] 1, [{Pt(bzq)(C≡CPh) 2 } 2 Pb] 2, and (NBu 4 ) [{Pt(bzq)) with that of the previously reported (NBu 4 ) 2 [{Pt(C 6 F 5 ) 4 } 2 Pb] 5 showed that the local environment of Pb II is highly sensitive to the nature of the anionic platinate(II) precursors. The photoluminescence (PL) studies of all 1-5 complexes revealed a dependence of PL on the structure type. Thus, complexes 1 and 5 exhibit metal centered emissions (1, 497 nm, 77 K; 5, 539 nm, φ ) 0.43, 298 K) related to the linear ( 5) or bent (1 Pt-Pb-Pt 149.9°) trinuclear entities. However, in complexes 2-4, that have unprecedented Pb II • • • η 1 (C≡CR) bonding interactions and very short Pt • • • Pb and Pt • • • Pt distances, the emissive state in solid state (77 K) is attributed to a 3 MLM′CT [Pt(1)π(C≡CR)fPt(2)/Pb(sp)π*(C≡CR)] state mixed with some ππ* excimeric character in neutral complexes 2 (R ) Ph) and 3 (R ) C 6 H 4 -CF 3 -4), and in the case of the adduct (NBu 4 )[{Pt(bzq)(C≡CC 6 H 4 -CF 3 -4) 2 } 2 Pb(O 2 ClO 2 )] 4 modified also by Pb II • • • O (O 2 ClO 2 -) contacts.chain. [25][26][27][28][29][30][31][32][33][34][35][36] Furthermore, the alkynyl ligands exhibit a very good π(η 2 ) coordinating capability, and we [37][38][39][40][41][42][43][44][45] and others [46][47][48][49][50][51][52][53] have demonstrated that the luminescence behavior is strongly influenced by perturbation of the electron density of the CtC unit through η 2 • • • metal alkynyl bonding and also by metallophilic interactions. [37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53] Homo and heteropolynuclear aggregates and clusters based on closed and/or subclosed-shell (d 8 , d 10 , d 10 s 2 ) metallic interactions [54][55][56][57][58] have also been studied as interesting emitters. [59][60][61][62][63][64][65][66][67][68][69][70][71][72][73] The presence of strong metallophilic interactions determines their structures and is often cited as an essential factor of their remarkable photophysical properties. [54][55][56][57][59][60][61][62][63][64][65][66][67][68][69][70][71][72][73] The arrangement of the metals and, in particular, the type of metals and coligands have a profound effect on the photophysical behavior of the resulting polynuclear systems. 61,74 Therefore, the controlled formation of novel polymetallic systems of the above metals and the study of their structure property correlations are of great importance in designing functional materials. Within this field, compared to the numerous reports involving polar M-Tl I54,

Two series of neutral luminescent pentafluorophenyl cycloplatinated­(II) complexes [Pt­(C^N)­(C6F5)­L] [C^N = C-deprotonated 2-phenylpyridine (ppy; a), 2-(2,4-difluorophenylpyridine (dfppy; b)] incorporating dimethyl sulfoxide [L = DMSO for 1 (1a reported by us in ref )] or biocompatible phosphine [L = PPh2C6H4COOH (dpbH; 2), PPh2C6H4CONHCH2COOMe (dpbGlyOMe; 3), P­(C6H4SO3Na)3 (TPPTS; 4)] ligands have been prepared and characterized and their optical properties studied. Their cytotoxic activities against tumor A549 (lung carcinoma), HeLa (cervix carcinoma), and nontumor NL-20 (lung epithelium) cell lines, as well as the ability to interact with DNA (plasmid pBR322), were evaluated. Complexes 2 exhibit higher cytotoxicity (IC50 3.89–20.29 μM) than compounds 1 (9.03–20.50 μM), whereas the activities of complexes 3 and 4 are negligible. All cytotoxic complexes show low selective toxicities toward cancer cells. Interestingly, except 1a, these complexes do not show evidence of DNA intercalation. Along the same lines, fluorescence costaining with Hoechst (2,5′-bi-1H-benzimidazole, 2′-(4-ethoxyphenyl)-5-(4-methyl-1-piperazinyl), a nuclear DNA stain) reveals that all complexes easily internalize, being mainly localized in the cytoplasm. In order to deepen the mechanism of biological action, the effect of the most cytotoxic complex 2b toward the dynamics of tubulin was explored. This complex displays tubulin depolymerization activity, exhibiting more potent inhibition of microtubule formation in A549 than in HeLa cells, in accordance with its higher antiproliferative activity (IC50 6.98 vs 12.45 μM), placing this complex as a potential antitubulin agent.

The anionic mixed species [trans-Pt(C6F5)2(C⋮CtBu)2]2- reacts with TlNO3 to yield the heteropolymetallic compound [PtTl2(C6F5)2(C⋮CtBu)2] (2). The X-ray crystal structure of its adduct {2(acetone)2} n shows its polymeric nature, giving the first example of a polymeric Pt(II)−Tl(I) complex stabilized by alkynyl−thallium and platinum−thallium bonding interactions. In the solid state, both 2 and the precursor (NBu4)2[trans-Pt(C6F5)2(C⋮CtBu)2] (1) exhibit photoluminescence at room temperature.

A new neutral cyclometalated platinum(II) solvate complex [cis-Pt(bzq)(C(6)F(5))(acetone)] (1) has been prepared by easy C-H activation of 7,8-benzo[h]quinoline on the coordination sphere of [cis-Pt(C(6)F(5))(2)(thf)(2)] (thf = tetrahydrofuran). The study of the reaction pathway has led us to the preparation of the bis(Hbzq) product [cis-Pt(C(6)F(5))(2)(Hbzq)(2)] (2) and the benzoquinoline-benzoquinolate derivative [Pt(bzq)(C(6)F(5))(Hbzq)] (3). This latter complex has been characterized by X-ray diffraction, showing the occurrence of π···π intermolecular stacking interactions associated to the deprotonated bzq units. The acetone molecule in [cis-Pt(bzq)(C(6)F(5))(acetone)] can be easily displaced by alkynes, allowing the synthesis of the first reported η(2)-alkyne-cycloplatinate complexes [Pt(bzq)(C(6)F(5))(η(2)-RC≡CR')] (R = H, R' = Ph 4, (t)Bu 5, Fc 6; R = R' = Ph 7), which have been fully characterized spectroscopically and by DFT studies. These alkyne complexes are only moderately stable in solution, and all attempts to obtain crystals suitable for X-ray diffraction were fruitless. Nevertheless, in the case of the ferrocenyl derivative, crystals of complex [Pt(κN:η(2)-bzq-C≡CFc)(C(6)F(5))(μ-κC(α):η(2)-C≡CFc)Pt(bzq)(C(6)F(5))] (8), containing an unusual alkynyl-functionalized benzoquinoline chelate ligand, were systematically obtained. All complexes (except those containing the ferrocenyl fragment) present emissive properties in solution and solid state (77 K), related, in general, with intraligand (bzq) excited states with some mixing (3)MLCT character, as supported by theoretical calculations. In solid state at room temperature, aggregation induced emission (AIE) is observed likely generated by intermolecular π···π stacking, as supporting by DFT calculations on 3(2). Interestingly, both types of excited states ((3)IL/(3)MLCT and AIE) seem to be close in energy in complexes 1 and 3, which show a significant luminescent thermochromism (green 77 K to orange 298 K).