Cyclometallated Pt(II) and Pd(II) complexes with a trithiacrown ligand

We report the synthesis and full characterization for a series of cyclometallated complexes of Pt(II) and Pd(II) incorporating the fluxional trithiacrown ligand 1,4,7-trithiacyclononane ([9]aneS3). Reaction of [M(C insertion mark N)(micro-Cl)]2 (M = Pt(II), Pd(II); C insertion mark N = 2-phenylpyridinate (ppy) or 7,8-benzoquinolinate (bzq)) with [9]aneS3 followed by metathesis with NH4PF6 yields [M(C insertion mark N)([9]aneS3)](PF6). The complexes [M(C insertion mark P)([9]aneS3)](PF6) (M = Pt(II), Pd(II); Cinsertion markP = [CH2C6H4P(o-tolyl)2-C,P]-) were synthesized from their respective [Pt(C insertion mark P)(micro-Cl)]2 or [Pd(C insertion mark P)(micro-O2CCH3)]2 (C insertion mark P) starting materials. All five new complexes have been fully characterized by multinuclear NMR, IR and UV-Vis spectroscopies in addition to elemental analysis, cyclic voltammetry, and single-crystal structural determinations. As expected, the coordinated [9]aneS3 ligand shows fluxional behavior in its NMR spectra, resulting in a single 13C NMR resonance despite the asymmetric coordination environment of the cyclometallating ligand. Electrochemical studies reveal irreversible one-electron metal-centered oxidations for all Pt(II) complexes, but unusual two-electron reversible oxidations for the Pd(II) complexes of ppy and bzq. The X-ray crystal structures of each complex indicate an axial M-S interaction formed by the endodentate conformation of the [9]aneS3 ligand. The structure of [Pd(bzq)([9]aneS3)](PF6) exhibits disorder in the [9]aneS3 conformation indicating a rare exodentate conformation as the major contributor in the solid-state structure. DFT calculations on [Pt([9]aneS3)(ppy)](PF6) and [Pd([9]aneS3)(ppy)](PF6) indicate the HOMO for both complexes is primarily dz2 in character with a significant contribution from the phenyl ring of the ppy ligand and p orbital of the axial sulfur donor. In contrast, the calculated LUMO is primarily ppy pi* in character for [Pt([9]aneS3)(ppy)](PF6), but dx2-y2 in character for [Pd([9]aneS3)(ppy)](PF6).     

Luminescent Benzoquinolate‐Isocyanide Platinum(II) Complexes: Effect of Pt⋅⋅⋅Pt and π⋅⋅⋅π Interactions on their Photophysical Properties

The neutral compounds [Pt(bzq)(CN)(CNR)] (R=tBu ( 1 ), Xyl ( 2 ), 2‐Np ( 3 ); bzq= benzoquinolate, Xyl=2,6‐dimethylphenyl, 2‐Np=2‐napthyl) were isolated as the pure isomers with a trans‐C_bzq,CNR configuration, as confirmed by ¹³C{¹H} NMR spectroscopy in the isotopically marked [Pt(bzq)(¹³CN)(CNR)] (R=tBu ( 1′ ), Xyl ( 2′ ), 2‐Np ( 3′ )) derivatives (δ¹³C_CN≈110 ppm; ¹J(Pt,¹³C)≈1425 Hz]. By contrast, complex [Pt(bzq)(C≡CPh)(CNXyl)] ( 4 ) with a trans‐N_bzq,CNR configuration, has been selectively isolated from [Pt(bzq)Cl(CNXyl)] (trans‐N_bzq,CNR) using Sonogashira conditions. X‐ray diffraction studies reveal that while 1 adopts a columnar‐stacked chain structure with Pt–Pt distances of 3.371(1) Å and significant π???π interactions (3.262 Å), complex 2 forms dimers supported only by short Pt???Pt (3.370(1) Å) interactions. In complex 4 the packing is directed by weak bzq???Xyl and bzq???C≡E (C, N) interactions. In solid state at room temperature, compounds 1 and 2 both show a bright red emission (?=42.1 % 1 , 57.6 % 2 ). Luminescence properties in the solid state at 77 K and concentration‐dependent emission studies in CH₂Cl₂ at 298 K and at 77 K are also reported for 1 , 1·CHCl3 , 2 , 2' , 2·CHCl3 , 3 , 4 .     

Highly luminescent half-lantern cyclometalated platinum(II) complex: synthesis, structure, luminescence studies, and reactivity

The half-lantern compound [{Pt(bzq)(μ-C(7)H(4)NS(2)-κN,S)}(2)]·Me(2)CO (1) was obtained by reaction of equimolar amounts of potassium 2-mercaptobenzothiazolate (KC(7)H(4)NS(2)) and [Pt(bzq)(NCMe)(2)]ClO(4). The Pt(II)···Pt(II) separation in the neutral complex [{Pt(bzq)(μ-C(7)H(4)NS(2)-κN,S)}(2)] is 2.910 (2) ?, this being among the shortest observed in half-lantern divalent platinum complexes. Within the complex, the benzo[h]quinoline (bzq) groups lie in close proximity with most C···C distances being between 3.3 and 3.7 ?, which is indicative of significant π-π interactions. The reaction of 1 with halogens X(2) (X(2) = Cl(2), Br(2), or I(2)) proceeds with a two-electron oxidation to give the corresponding dihalodiplatinum(III) complexes [{Pt(bzq)(μ-C(7)H(4)NS(2)-κN,S)X}(2)] (X = Cl 2, Br 3, I 4). Their X-ray structures confirm the retention of the half-lantern structure and the coordination mode of the bzq and the bridging ligand μ-C(7)H(4)NS(2)-κN,S. The Pt-Pt distances (Pt-Pt = 2.6420(3) ? 2, 2.6435(4) ? 3, 2.6690(3) ? 4) are shorter than that in 1 because of the Pt-Pt bond formation. Time dependent-density functional theory (TD-DFT) studies performed on 1 show a formal bond order of 0 between the metal atoms, with the 6p(z) contribution diminishing the antibonding character of the highest occupied molecular orbital (HOMO) and being responsible for an attractive intermetallic interaction. A shortening of the Pt-Pt distance from 2.959 ? in the ground state S(0) to 2.760 ? in the optimized first excited state (T(1)) is consistent with an increase in the Pt-Pt bond order to 0.5. In agreement with TD-DFT calculations, the intense, structureless, red emission of 1 in the solid state and in solution can be mainly attributed to triplet metal-metal-to-ligand charge transfer ((3)MMLCT) [dσ*(Pt-Pt) → π*(bzq)] excited states. The high quantum yields of this emission measured in toluene (44%) and solid state (62%) at room temperature indicate that 1 is a very efficient and stable (3)MMLCT emitter, even in solution. The high luminescence quantum yield of its red emission, added to its neutral character and the thermal stability of 1, make it a potential compound to be incorporated as phosphorescent dopant in multilayer organic light-emitting devices (OLEDs).     

Synthesis, structural characterization, and photophysical properties of palladium and platinum(II) complexes containing 7,8-benzoquinolinate and various phosphine ligands

A series of mononuclear cyclometalated benzo[h]quinolinate platinum and palladium(II) complexes with phosphine ligands, namely, [M(bzq)ClL] (L=PPh2H, Pt 1, Pd 2; PPh2CCPh, Pt 3, Pd 4), [Pt(bzq)(PPh2H)(PPh2CCPh)]ClO4 5, [Pt(bzq)(PPh2C(Ph)=C(H)PPh2)]ClO4 6, and [Pt(bzq)(CCPh)(PPh2CCPh)] (7a, 7b), were synthesized. The X-ray crystal structures of 1, 6.CH3COCH3.1/2CH3(CH2)4CH3, and 7b.CH3COCH3 have been determined. In 1, the metalated carbon atom and the P atom are mutually cis, whereas in 7b they are trans located. For complex 6, C and N are crystallographically indistinguishable. Reaction of [Pt(bzq)(mu-Cl)]2 with PPh2H and excess of NEt3 leads to the phosphide-bridge platinum dimer [Pt(bzq)(mu-PPh2)]2 8 (X-ray). Moderate pi-pi intermolecular interactions and no evident Pt-Pt interactions are found in 1, 7b, and in 8. All of the complexes exhibit absorption bands at high energy due to the intraligand transitions (1IL pi --> pi) and absorptions at lower energy which are attributed to MLCT (5d) pi --> pi (CLambdaN) transition. Platinum complexes show strong luminescence in both solid state and frozen solutions. The influence of the coligands on the photophysics of the platinum complexes has been examined by absorption and emission spectroscopy.     

Pt-Ag clusters and their neutral mononuclear Pt(II) starting complexes: structural and luminescence studies

The mononuclear complexes [Pt(bzq)(S^S)] [S^S = pyrrolidinedithiocarbamate (pdtc 1), dimethyldithiocarbamate (dmdtc 2)] were prepared by reaction of [Pt(bzq)(NCMe)(2)]ClO(4) with an equimolecular amount of [NH(4)(pdtc)] and [Na(dmdtc)·2H(2)O] respectively in MeOH. Reactions of 1 and 2 with AgClO(4) in 1 : 1 and 2 : 1 molar ratios rendered the heteropolinuclear compounds [{Pt(bzq)(S^S)Ag}(2)](ClO(4))(2) (S^S = pdtc 3, dmdtc 4) and [{Pt(bzq)(S^S)}(2)Ag](ClO(4)) (S^S = pdtc 5, dmdtc 6) respectively. The X-ray studies on single crystals of 3 and 4 showed that both consist of tetranuclear [Pt(2)Ag(2)] clusters with the Pt-Ag and the Ag-Ag distances in the range of those corresponding to Pt-Ag dative bonds and argentophilic interactions. In 3 the tetranuclear [Pt(2)Ag(2)] clusters are connected into infinite polymeric chains by Pt···Pt metallophilic interactions (Pt···Pt = 3.1890(7) ?). The X-ray study on a single crystal of 5 showed that it is a polymer based on trinuclear [Pt(2)Ag] clusters containing two unsupported Pt-Ag dative bonds and connected by Ag-S bonds in such a way that the "Pt-Ag-S-Pt-Ag-S" atoms draw a zigzag polymeric chain. TD-DFT calculations carried out for 1 indicate that the lowest energy absorption band in CH(2)Cl(2) can be described as a mixture of (1)MLCT, (1)IL and (1)L'LCT transitions. Powdered samples of 1 at 298 K and 77 K show a green-yellow emission band coming mainly from a (3)LC excited state. However complex 2 shows "luminescence thermochromism": the colour of its luminescence changes from green-yellow at 77 K to orange-red at 298 K. The emission of the Pt-Ag clusters, 3-6, in the solid state, are due to excimeric (3)ππ and/or (3)MMLCT (dσ* →π*) low-lying excited states, indicating that the presence of silver in the clusters makes the "Pt(bzq)(S^S)" fragments interact to a large extent through Pt···Pt and/or π-π interactions. Solid 3 is a highly selective vapochromic compound towards acetonitrile although this behaviour is not fully reversible.     

Benzoquinolateplatinum(II) complexes as building blocks in the synthesis of Pt-Ag extended structures

The reaction between (NBu(4))[Pt(bzq)(C(6)F(5))(2)] (1, bzq = 7,8-benzoquinolate) and AgClO(4) in a 1 : 1 molar ratio, in acetone, gives the polymer [{Pt(bzq)(C(6)F(5))(2)}Ag](n) (2). The reaction of 2 with equimolecular amounts of PPh(3) and SC(4)H(8) (tht) produces the bimetallic complexes [{Pt(bzq)(C(6)F(5))(2)}AgL] (L = PPh(3) (3), tht (4)). For L = py, decomposition takes place and [Pt(bzq)(C(6)F(5))py] (5) is obtained. All these complexes have been characterized by X-ray diffraction. The most interesting features of complexes 2-4 is the presence of Pt-Ag bonds, with Pt-Ag distances of ca. 2.75 ?. Besides, the silver centres establish short η(1) bonding interactions with the C(ipso) of the bzq ligands, with distances Ag-C of ca. 2.45 ?. Complex 2 is a one-dimensional infinite chain in which the fragments "Pt(bzq)(C(6)F(5))(2)(-)" and Ag(+) alternate. On the other hand, complexes 1 and 3-5 show intermolecular pairing through π···π interactions between the aromatic rings of the bzq ligand, having interplanar separations of ca. 3.5 ?. Complex 2 dissolves in donor solvents (acetone, THF) as discrete bimetallic solvated fragments [{Pt(bzq)(C(6)F(5))(2)}AgS(n)] (S = solvent), similar to complexes 3 and 4. The persistence of the Pt-Ag bond in 2-4, supported by multinuclear NMR spectroscopy, causes a significant blue-shift in the lowest-lying absorption in relation to 1. This fact is attributed (TD-DFT) to a remarkable modification of the orbitals contributing to the HOMO, which changes the character of the transition from (1)LC/(1)MLCT in 1 to admixture (1)L'LCT/(1)MLCT in the bimetallic complexes. The low energy feature (490-530 nm) of 2 in solid state is attributed to CT from the Pt fragments to the Ag centers. Complexes 2-4 are only emissive in rigid media (solid and glasses). In the solid state, the metallic chain 2 exhibits a bright orange emission (560 nm, 298 K; 590 nm, 77 K), assigned to an excited state involving charge transfer from the platinum fragment with a remarkable contribution of C(6)F(5) (Ar(f)) rings to the Pt-Ag bond ((3)LMM'CT/(3)L'M'CT). However, 3 and 4 exhibit in solid state at 298 K a vibronic band, which is clearly resolved in two close non-equilibrated bands at 77 K in 3, tentatively ascribed to a mixture of (3)MLCT/(3)L'LCT transitions modified by the formation of the Pt-Ag bond. In glassy solution (77 K) 2-4 display a vibronic emission ascribed primarily to (3)LC character.     

Metal-metal interactions in thallium(I)/platinum(II) compounds involving a chelating dicarbene and various auxiliary ligands

Reaction of Tl(I)NO(3) and (C(4)H(10)N(4))Pt(II)(mnt) or (C(4)H(10)N(4))Pt(II)(dmg-H) [mnt = maleonitriledithiolate, dmg-H = dimethylglyoximate dianion] in dilute, aqueous KOH yielded adducts of Tl(I) and the conjugate bases of the platinum(II) compounds. The compound Tl(I)[(C(4)H(9)N(4))Pt(II)(dmg-H)].5H(2)O forms as dimers with close Tl(I)...Pt(II) separations of 3.0843(5) A, while Tl(I)[(C(4)H(9)N(4))Pt(II)(mnt)] has much longer Tl(I)...Pt(II) separations of 3.4400(2) A and forms loosely associated, helical coordination polymers. The new compounds are compared with the red and yellow polymorphs of Tl(I)[(C(4)H(9)N(4))Pt(II)(CN)(2)], and the influences of crystal packing forces, Coulombic interactions, and hydrogen bonding on supramolecular structures and Tl(I)...Pt(II) separations are discussed.     

Crystal structure and optical spectroscopy of Er2[Pt(CN)4]3.21H2O and Er2[Pt(CN)4]2.SO4.11.5H2O

We have synthesized two forms of erbium tetracyanoplatinates, Er2[Pt(CN)4]3.21H2O (red form) and Er2[Pt(CN)4]2.SO4.11.5H2O (yellow form), and determined their crystal structures by X-ray diffraction. While the red form crystallizes in the orthorhombic space group Pbcn, with a = 15.4848(3) A, b = 13.8186(2) A, c = 19.07820(10) A, alpha = beta = gamma = 90 degrees, and Z = 4, the yellow form precipitates in the tetragonal space group I4cm, with a = b = 14.321(2) A, c = 13.338(3) A, alpha = beta = gamma = 90 degrees, and Z = 4. Both forms show [Pt(CN)4]2- chains but differ markedly in color and morphology. This is due to the incorporation of sulfate ions in the latter modification, leading to an increased Pt-Pt distance. The observed optical absorption and emission behavior of the title compounds is correlated with the Pt-Pt distances.     

Iodide, azide, and cyanide complexes of (N,C), (N,N), and (N,O) metallacycles of tetra- and pentavalent uranium

In contrast to the neutral macrocycle [UN*(2)(N,C)] (1) [N* = N(SiMe(3))(3); N,C = CH(2)SiMe(2)N(SiMe(3))] which was quite inert toward I(2), the anionic bismetallacycle [NaUN*(N,C)(2)] (2) was readily transformed into the enlarged monometallacycle [UN*(N,N)I] (4) [N,N = (Me(3)Si)NSiMe(2)CH(2)CH(2)SiMe(2)N(SiMe(3))] resulting from C-C coupling of the two CH(2) groups, and [NaUN*(N,O)(2)] (3) [N,O = OC(═CH(2))SiMe(2)N(SiMe(3))], which is devoid of any U-C bond, was oxidized into the U(V) bismetallacycle [Na{UN*(N,O)(2)}(2)(μ-I)] (5). Sodium amalgam reduction of 4 gave the U(III) compound [UN*(N,N)] (6). Addition of MN(3) or MCN to the (N,C), (N,N), and (N,O) metallacycles 1, 4, and 5 led to the formation of the anionic azide or cyanide derivatives M[UN*(2)(N,C)(N(3))] [M = Na, 7a or Na(15-crown-5), 7b], M[UN*(2)(N,C)(CN)] [M = NEt(4), 8a or Na(15-crown-5), 8b or K(18-crown-6), 8c], M[UN*(N,N)(N(3))(2)] [M = Na, 9a or Na(THF)(4), 9b], [NEt(4)][UN*(N,N)(CN)(2)] (10), M[UN*(N,O)(2)(N(3))] [M = Na, 11a or Na(15-crown-5), 11b], M[UN*(N,O)(2)(CN)] [M = NEt(4), 12a or Na(15-crown-5), 12b]. In the presence of excess iodine in THF, the cyanide 12a was converted back into the iodide 5, while the azide 11a was transformed into the neutral U(V) complex [U(N{SiMe(3)}SiMe(2)C{CHI}O)(2)I(THF)] (13). The X-ray crystal structures of 4, 7b, 8a-c, 9b, 10, 12b, and 13 were determined.     

Theoretical studies on structures and spectroscopic properties of a series of novel mixed-ligand Ir(III) complexes [Ir(Mebib)(ppy)X

The series of novel mixed-ligand iridium(III) complexes Ir(Mebib)(ppy)X (Mebib = bis(N-methylbenzimidazolyl)benzene and ppy = phenylpyridine; X = Cl, 1; X = -C[triple band]CH, 2; X = CN, 3) have been investigated theoretically to explore their electronic structures and spectroscopic properties. The ground and excited state geometries have been fully optimized at the B3LYP/LANL2DZ and CIS/LANL2DZ levels, respectively. The optimized geometry structural parameters agree well with the corresponding experimental results. The HOMO of 1 and 3 are mainly localized on the Ir atom, Mebib, and ppy ligand, but that of 2 has significant X ligand composition. Absorptions and phosphorescences in CH2 Cl2 media have been calculated using the TD-DFT level of theory with the PCM model based on the optimized ground and excited state geometries, respectively. The lowest lying absorptions of 1 and 3 at 444 and 416 nm are attributed to a {[d(yz)(Ir) + pi(Mebib) + pi(ppy)] --> [pi*(Mebib)]} transition with metal-to-ligand, ligand-to-ligand, and intra-ligand charge transfer (MLCT/LLCT/ILCT) character, whereas that of 2 at 458 nm is related to a {[d(yz)(Ir) + pi(Mebib) + pi(ppy) + pi(C[triple band]CH)] --> [pi*(Mebib)]} transition with MLCT/LLCT/ILCT and X ligand-to-ligand charge transfer (XLCT) transition character. The phosphorescence of 1 and 3 at 565 and 543 nm originates from the 3{[dy(yz)(Ir) + pi(Mebib) + pi(ppy)] [pi*(Mebib)]} excited state, while that of 2 at 576 nm originates from the 3{[d(yz)(Ir) + pi(Mebib) + pi(ppy) + pi(C[triple band]CH)] [pi*(Mebib)]} excited state. The calculation results show that the absorption and emission transition character can be changed by altering the pi electron-withdrawing ability of the X ligand and the phosphorescent color can be tuned by adjusting the X ligand.     

Synthesis and photophysical properties of cyclometalated platinum(II) 1,2-benzenedithiolate complexes and heterometallic derivatives obtained from the addition of [Au(PCy3)]+ units

The cyclometalated compounds [Pt(C^N)(HC^N)Cl] [HC^N = 2-phenylpyridine (Hppy; 1a), 1-(4-tert-butylphenyl)isoquinoline (Htbpiq; 1b)] react with 1,2-benzenedithiol, t-BuOK, and Bu(4)NCl in a 1:1:2:1 molar ratio in CH(2)Cl(2)/MeOH to give the complexes Bu(4)N[Pt(C^N)(bdt)] [bdt = 1,2-benzenedithiolate; C^N = ppy (Bu(4)N2a), tbpiq (Bu(4)N2b)]. In the absence of Bu(4)NCl, the same reactions afford solutions of K2a and K2b, which react with [AuCl(PCy(3))] to give the neutral heterometallic derivatives [Pt(C^N)(bdt){Au(PCy(3))}] [C^N = ppy (3a), tbpiq (3b)]. The cationic derivatives [Pt(C^N)(bdt){Au(PCy(3))}(2)]ClO(4) [C^N = ppy (4a), tbpiq (4b)] are obtained by reacting 3a and 3b with acetone solutions of [Au(OClO(3))(PCy(3))]. The crystal structures of 3b and 4b reveal the formation of short Pt···Au metallophilic contacts in the range 2.929-3.149 ?. Complexes 3b, 4a, and 4b undergo dynamic processes in solution that involve the migration of the [Au(PCy(3))](+) units between the S atoms of the dithiolate. Complexes Bu(4)N2a and 2b display a moderately solvatochromic band in their electronic absorption spectra that can be ascribed to a transition of mixed ML'CT/LL'CT character (M= metal; L = bdt; L' = C^N; CT = charge transfer), while their emissions are assignable to transitions of the same orbital parentage but from triplet excited states. The successive addition of [Au(PCy(3))](+) units to the anions 2a and 2b results in an increase in the absorption and emission energies attributable to lower highest occupied molecular orbital energies. Additionally, the characteristics of the absorption and emission spectra of the heterometallic derivatives indicate a gradual loss of LL'CT character in the involved electronic transitions, with a concomitant increase of the L'C and ML'CT contributions.     

Thermal and photo control of the linkage isomerism of bis(thiocyanato)(2,2'-bipyridine)platinum(II)

Three linkage isomers, bis(thiocyanato-S)(2,2'-bipyridine)platinum(II) ([Pt(SCN)(2)(bpy)]), (thiocyanato-S)(thiocyanato-N)(2,2'-bipyridine)platinum(II) ([Pt(SCN)(NCS)(bpy)]), and bis(thiocyanato-N)(2,2'-bipyridine)platinum(II) ([Pt(NCS)(2)(bpy)]) were isolated, and their structures were elucidated. The crystal data are as follows: for [Pt(SCN)(2)(bpy)], C(12)H(8)N(4)S(2)Pt, orthorhombic, P2(1)2(1)2(1) (No. 19), a = 12.929(9) A, b = 18.67(1) A, c = 5.497(4) A, Z = 4; for [Pt(SCN)(NCS)(bpy)], C(12)H(8)N(4)S(2)Pt, monoclinic, P2(1)/n (No. 14), a = 10.909(7) A, b = 7.622(4) A, c = 16.02(1) A, beta = 102.323(7) degrees, Z = 4; for [Pt(NCS)(2)(bpy)], C(12)H(8)N(4)S(2)Pt, orthorhombic, Pbcm (No. 57), a = 10.3233(8) A, b = 19.973(2) A, c = 6.4540(5) A, Z = 4. The stacking structures of the isomers were found to be different depending on the coordination geometries based on the N- and S-coordination of the thiocyanato ligands, which control the color and luminescence of the crystals sensitively. The isomerization behaviors of the complex have been investigated both in solution and in the solid state. In solution, stepwise thermal isomerization from [Pt(SCN)(2)(bpy)] to [Pt(NCS)(2)(bpy)] by way of [Pt(SCN)(NCS)(bpy)] was observed using (1)H NMR spectroscopy. Reverse isomerization, from [Pt(NCS)(2)(bpy)] to [Pt(SCN)(NCS)(bpy)] and [Pt(SCN)(2)(bpy)], occurred when irradiated with near ultraviolet (UV) light. In contrast, the [Pt(SCN)(2)(bpy)] yellow crystals exhibited thermal isomerization directly to red crystals of [Pt(NCS)(2)(bpy)], as detected by changes in the emission spectrum, which indicates that the flip of two SCN(-) ligands correlatively occurred in the solid state. The yellow crystals of [Pt(SCN)(NCS)(bpy)] were also converted to the thermodynamically stable red crystal of [Pt(NCS)(2)(bpy)] though the reverse isomerization has never been observed to occur by photoirradiation in the solid state.     

Syntheses and characterization of the metal maleonitrilediselenolates [K([2.2.2]-cryptand)]2[M(Se2C2(CN)2)2] (M = Ni, Pd, Pt) and [Ni(dmf)(5)Cl]2[Ni(Se2C2(CN)2)2

Reaction of KNH(2), K(2)Se, Se, [2.2.2]-cryptand, and a metal source yields the metal bis(maleonitrilediselenolates) [K([2.2.2]-cryptand)](2)[M(Se(2)C(2)(CN)(2))(2)] (M = Ni, 1; Pd, 2, Pt, 3). These compounds are isostructural and crystallize with four formula units in the monoclinic space group P2(1)/c in cells at T = 153 K with parameters (a (A), b (A), c (A), beta (deg), V (A(3))) of 12.220(1), 15.860(2), 15.306(1), 107.64(2), 2827(1) for 1; 12.291(1), 15.669(1), 15.548(1), 108.55(1), 2839(1) for 2; and 12.292(3), 15.671(3), 15.569(3), 108.59(3), 2842(1) for 3. The cation of 1 has been substituted to yield [Ni(dmf)(5)Cl](2)[Ni(Se(2)C(2)(CN)(2))(2)] (4). [Ni(dmf)(5)Cl](2)[Ni(Se(2)C(2)(CN)(2))(2)] (4) crystallizes with one molecule in the triclinic space group P1 in a cell with parameters (T = 153 K) of a = 8.842(2) A, b =13.161(3) A, c = 13.831(3) A, alpha = 110.08(3) degrees, beta = 95.23(3) degrees, gamma = 93.72(3) degrees, V = 1484(1) A(3). The electronic absorption and infrared spectra are characteristic of metal maleonitrilediselenolates. Cyclic voltammetry shows that the maleonitrilediselenolate (mns) complexes are more easily oxidized than their maleonitriledithiolate (mnt) analogues.     

Pt]2Pb trinuclear systems: impact of the anionic platinum fragment on the lead environment and photoluminescence

A comparison of the solid structures of three novel trinuclear sandwich Pt 2Pb systems (NBu 4) 2[{Pt(C identical withCTol) 4} 2Pb(OH 2) 2] 1, [{Pt(bzq)(C identical withCPh) 2} 2Pb] 2, and (NBu 4)[{Pt(bzq)(C identical withCC 6H 4-CF 3-4) 2} 2Pb(O 2ClO 2)] 4 (NBu 4[ 3.(O 2ClO 2)]) with that of the previously reported (NBu 4) 2[{Pt(C 6F 5) 4} 2Pb] 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, varphi = 0.43, 298 K) related to the linear ( 5) or bent ( 1 Pt-Pb-Pt 149.9 degrees ) trinuclear entities. However, in complexes 2- 4, that have unprecedented Pb (II)...eta (1)(C identical withCR) 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)pi(C identical withCR)-->Pt(2)/Pb(sp)pi*(C identical withCR)] state mixed with some pipi* excimeric character in neutral complexes 2 (R = Ph) and 3 (R = C 6H 4-CF 3-4), and in the case of the adduct (NBu 4)[{Pt(bzq)(C identical withCC 6H 4-CF 3-4) 2} 2Pb(O 2ClO 2)] 4 modified also by Pb (II)...O (O 2ClO 2 (-)) contacts.     

Pyrazolylborates and their importance in tuning single-molecule magnet properties of {Fe(III)2Ni(II)} complexes

A new tricyanoferrate(III) building block and a trinuclear single-molecule magnet derivative are described. The treatment of a 2:1 ratio of [NEt(4)][(Tp*(Bn))Fe(III)(CN)(3)]·H(2)O·MeOH [1; Tp*(Bn) = tris(3,5-dimethyl-4-benzyl)pyrazolylborate] with nickel(II) trifluoromethanesulfonate gives {[(Tp*(Bn))Fe(III)(CN)(3)](2)[Ni(II)(DMF)(4)]}·2DMF (2; DMF = N,N-dimethylformamide). The symmetry-equivalent Fe(III)(LS) ions lead to a favorable alignment of anisotropy tensors (i.e., Fe···B axes) in 2, and an energy barrier of Δ(eff)/k(B) = 16.7 K is found for the S(T) = 2 complex.     

1,12-Diazaperylene and 2,11-dialkylated-1,12-diazaperylene iridium(iii) complexes [Ir(C^N)(2)(N^N)]PF(6): new supramolecular assemblies

A series of new monocationic iridium(iii) complexes [Ir(C^N)(2)(N^N)]PF(6) with "large-surface"α,α'-diimin ligands N^N (dap = 1,12-diazaperylene, dmedap = 2,11-dimethyl-1,12-diazaperylene, dipdap = 2,11-diisopropyl-1,12-diazaperylene) and different cyclometalating ligands C^N (piq = 1-phenylisoquinoline, bzq = benzo[h]quinoline, ppz = 1-phenylpyrazole, thpy = 2-(2-thienyl)pyridine, ppy = 2-phenylpyridine, meppy = 2-(4-methylphenyl)pyridine, dfppy = 2-(2,4-difluorophenyl)pyridine) were synthesized. The solid structures of the complexes [Ir(piq)(2)(dap)]PF(6), [Ir(bzq)(2)(dap)]PF(6), [Ir(ppy)(2)(dipdap)]PF(6), [Ir(piq)(2)(dmedap)]PF(6), [Ir(ppy)(2)(dap)]PF(6) and [Ir(ppz)(2)(dap)]PF(6) are reported. In [Ir(piq)(2)(dap)]PF(6), the dap ligand and one of the piq ligands of each cationic complex are involved in π-π stacking interactions forming supramolecular channels running along the crystallographic c axis. In the crystalline [Ir(bzq)(2)(dap)]PF(6)π-π stacking interactions between the metal complexes lead to the formation of a 2D layer structure. In addition, CH-π interactions were found in all compounds, which are what stabilizes the solid structure. In particular, a significant number of them were found in [Ir(piq)(2)(dap)]PF(6) and [Ir(bzq)(2)(dap)]PF(6). The crystal structures of [Ir(ppy)(2)(dipdap)]PF(6) and [Ir(ppy)(2)(dmedap)]PF(6) are also presented, being the first examples of bis-cyclometalated iridium(iii) complexes with phenanthroline-type α,α'-diimin ligands bearing bulky alkyl groups in the neighbourhood of the N-donor atoms. These ligands implicate a distorted octahedral coordination geometry that in turn destabilized the Ir-N(N^N) bonds. The new iridium(iii) complexes are not luminescent. All compounds show an electrochemically irreversible anodic peak between 1.15 and 1.58 V, which is influenced by the different cyclometalated ligands. All of the new complexes show two reversible successive one-electron "large-surface" ligand-centred reductions around -0.70 V and -1.30 V. Electrospray ionisation mass spectrometry (ESI-MS) and collision induced decomposition (CID) measurements were used to investigate the stability of the new complexes. Thereby, the stability agreed well with the order of the Ir-N(N^N) bond lengths.     

Highly phosphorescent iridium complexes containing both tridentate bis(benzimidazolyl)-benzene or -pyridine and bidentate phenylpyridine: synthesis, photophysical properties, and theoretical study of Ir-bis(benzimidazolyl)benzene complex

Novel mixed-ligand Ir(III) complexes, [Ir(L)(NwedgeC)X]n+ (L = N/\C/\N or N/\N/\N; X = Cl, Br, I, CN, CH3CN, or -CCPh; n = 0 or 1), were synthesized, where N/\CwedgeN = bis(N-methylbenzimidazolyl)benzene (Mebib) and bis(N-phenylbenzimidazolyl)benzene (Phbib), N/\N/\N = bis(N-methylbenzimidazolyl)pyridine (Mebip), and N/\C = phenylpyridine (ppy) derivatives. The X-ray crystal structures of [Ir(Phbib)(ppy)Cl] and [Ir(Mebib)(mppy)Cl] [mppy = 5-methyl-2-(2'-pyridyl)phenyl] indicate that the nitrogen atom of the ppy ligand is located trans to the coordinating carbon atom in Me- or Phbib, while the coordinating carbon atom in ppy occupies the trans position of Cl. [Ir(Mebip)(ppy)Cl]+ showed a quasireversible Ir(III/IV) oxidation wave at +1.05 V, while the Ir complexes, [Ir(Mebib)(ppy)Cl], were oxidized at +0.42 V versus Fc/Fc+. The introduction of an Ir-C bond in [Ir(Mebib)(ppy)Cl] induces a large potential shift of 0.63 V in a negative direction. Further, the oxidation potential of [Ir(Mebib)(Rppy)X] was altered by the substitution of R, R', and X groups. Compared to the oxidation potential, the first reduction potential revealed an almost constant value at -2.36 to -2.46 V for [Ir(L)(ppy)Cl] (L = Mebib and Phbib) and -1.52 V for [Ir(Mebip)(ppy)Cl. The UV-vis spectra of [Ir(Mebib)(R-ppy)X] show a clear singlet metal-to-ligand charge-transfer transition around 407 approximately 425 nm and a triplet metal-to-ligand charge-transfer transition at 498 approximately 523 nm. [Ir(Mebip)(ppy)Cl]+ emits at 610 nm with a luminescent quantum yield of Phi = 0.16 at room temperature. The phosphorescence of [Ir(Mebib)(ppy)X] was observed at 526 nm for X = CN and 555 nm for X = Cl with the high luminescent quantum yields, Phi = 0.77 approximately 0.86, at room temperature. [Ir(Phbib)(ppy)Cl] shows the emission at 559 nm with a luminescent quantum yield of Phi = 0.95, which is an unprecedentedly high value compared to those of other emissive metal complexes. Compared to the luminescent quantum yields of the Ir(ppy)2(L) derivatives and [Ir(Mebip)(ppy)Cl]+, the neutral Ir complexes, [Ir(L)(R-ppy)X] (L = Me- or Phbib), reveal very high quantum yields and large radiative rate constants (kr) ranging from 3.4 x 10(5) to 5.5 x 10(5) s(-1). The density functional theory calculation suggests that these Ir complexes possess dominantly metal-to-ligand charge-transfer and halide-to-ligand charge-transfer excited states. The mechanism for a high phosphorescence yield in [Ir(bib)(ppy)X] is discussed herein from the perspective of the theoretical consideration of radiative rate constants using perturbation theory and a one-center spin-orbit coupling approximation.     

New structural features of unsupported chains of metal ions in luminescent [(NH3)4Pt][Au(CN)2]2 x 1.5(H2O) and related salts

Luminescent [(NH(3))(4)Pt][Au(CN)(2)](2).1.5(H(2)O), which forms from aqueous solutions of [(NH(3))(4)Pt]Cl(2) and K[Au(CN)(2)], crystallizes with extended chains of the two ions with multiple close Pt...Au (3.2804(4) and 3.2794(4) A) and Au...Au (3.2902(5), 3.3312(5), and 3.1902(4) A) contacts. Nonluminescent [(NH(3))(4)Pt][Ag(CN)(2)](2).1.4(H(2)O) is isostructural with [(NH(3))(4)Pt][Au(CN)(2)](2).1.5(H(2)O). Treatment of [(NH(3))(6)Ni]Cl(2) with K[Au(CN)(2)] forms [(NH(3))(2)Ni][Au(CN)(2)](2) in which the [Au(CN)(2)](-) ions function as nitrile ligands toward nickel, which assumes a six-coordinate structure with trans NH(3) ligands. The [Au(CN)(2)](-) ions self-associate into linear columns with close Au...Au contacts of 3.0830(5) A, and pairs of gold ions in these chains make additional but longer (3.4246(5) A) contacts with other gold ions.     

Stable diplatinum complexes with functional thiolato bridges from dialkylation of [Pt2(mu-S)2(P-P)2] [P-P=2 x PPh3, Ph2P(CH2)3PPh2

The normally robust monoalkylated complexes [Pt(2)(mu-S)(mu-SR)(PPh(3))(4)](+) can be activated towards further alkylation. Dialkylated complexes [Pt(2)(mu-SR)(2)(P-P)(2)](2+) (P-P=2 x PPh(3), Ph(2)P(CH(2))(3)PPh(2)) can be stabilized and isolated by the use of electron-rich and aromatic halogenated substituents R [e.g. 3-(2-bromoethyl)indole and 2-bromo-4'-phenylacetophenone] and 1,3-bis(diphenylphosphino)propane [Ph(2)P(CH(2))(3)PPh(2) or dppp] which enhances the nucleophilicity of the {Pt(2)(mu-S)(2)} core. This strategy led to the activation of [Pt(2)(mu-S)(mu-SR)(PPh(3))(4)](+) towards R-X as well as isolation and crystallographic elucidation of [Pt(2)(mu-SC(10)H(10)N)(2)(PPh(3))(4)](PF(6))(2) (2a), [Pt(2)(mu-SCH(2)C(O)C(6)H(4)C(6)H(5))(2)(PPh(3))(4)](PF(6))(2) (2b), and a range of functionalized-thiolato bridged complexes such as [Pt(2)(mu-SR)(2)(dppp)(2)](PF(6))(2) [R= -CH(2)C(6)H(5) (8a), -CH(2)CHCH(2) (8b) and -CH(2)CN (8c)]. The stepwise alkylation process is conveniently monitored by Electrospray Ionisation Mass Spectrometry, allowing for a direct qualitative comparison of the nucleophilicity of [Pt(2)(mu-S)(2)(P-P)(2)], thereby guiding the bench-top synthesis of some products observed spectroscopically.     

Binuclear cyclometalated organoplatinum complexes containing 1,1'-bis(diphenylphosphino)ferrocene as spacer ligand: kinetics and mechanism of MeI oxidative addition

The binuclear complex [Pt2Me2(ppy)2(mu-dppf)], 1, in which ppy = deprotonated 2-phenylpyridyl and dppf = 1,1'-bis(diphenylphosphino)ferrocene, was synthesized by the reaction of [PtMe(SMe2)(ppy)] with 0.5 equiv of dppf at room temperature. In this reaction when 1 equiv of dppf was used, the dppf chelating complex 2, [PtMe(dppf)(ppy-kappa1C)], was obtained. The reaction of Pt(II)-Pt(II) complex 1 with excess MeI gave the Pt(IV)-Pt(IV) complex [Pt2I2Me4(ppy)2(mu-dppf)], 3. When the reaction was performed with 1 equiv of MeI, a mixture containing unreacted complex 1, a mixed-valence Pt(II)-Pt(IV) complex [PtMe(ppy)(mu-dppf)PtIMe2(ppy)], 4, and complex 3 was obtained. In a comparative study, the reaction of [PtMe(SMe2)(ppy)] with 1 equiv of monodentate phosphine PPh3 gave [PtMe(ppy)(PPh3)], A. MeI was reacted with A to give the platinum(IV) complex [PtMe2I(ppy)(PPh3)], C. All the complexes were fully characterized using multinuclear (1H, 31P, 13C, and 195Pt) NMR spectroscopy, and complex 2 was further identified by single crystal X-ray structure determination. The reaction of binuclear Pt(II)-Pt(II) complex 1 with excess MeI was monitored by low temperature 31P NMR spectroscopy and further by 1H NMR spectroscopy, and the kinetics of the reaction was studied by UV-vis spectroscopy. On the basis of the data, a mechanism has been suggested for the reaction which overall involved stepwise oxidative addition of MeI to the two Pt(II) centers. In this suggested mechanism, the reaction proceeded through a number of Pt(II)-Pt(IV) and Pt(IV)-Pt(IV) intermediates. Although MeI in each step was trans oxidatively added to one of the Pt(II) centers, further trans to cis isomerizations of Me and I groups were also identified. A comparative kinetic study of the reaction of monomeric platinum(II) complex A with MeI was also performed. The rate of reaction of MeI with complex 1 was some 3.5 times faster than that with complex A, indicating that dppf in the complex 1, as compared with PPh 3 in the complex A, has significantly enhanced the electron richness of the platinum centers.