Preparation, spectroscopy, X-ray analysis, and water-solubility studies of the first bis-PTA (PTA = 1,3,5-triaza-7-phosphaadamantane) derivatives

The bis-phosphines, 1,1′-[1,2-phenylenebis(methylene)]bis-3,5-diaza-1-azonia-7-phosphatricyclo[3.3.1.1]decane dibromide (1), 1,1′-[1,3-arenebis(methylene)]bis-[3,5-diaza-1-azonia-7-phosphatricyclo [3.3.1.1]decane dibromide (arene = phenyl (2), tolyl (3), anisolyl (4)), and 1,1′-[1,4-phenylenebis(methylene)]bis-3,5-diaza-1-azonia-7-phosphatricyclo[3.3.1.1]decane dibromide (5) were prepared in over 90% yield by refluxing 1,2-bis(bromomethyl)benzene, 1,3-bis(bromomethyl)benzene, 1,3-bis(bromomethyl)-5-methyl-benzene, 1,3-bis(bromomethyl)-5-methoxy-benzene, and 1,4-bis(bromomethyl)benzene with 1,3,5-triaza-7-phosphaadamantane (PTA) in acetone or chloroform. Compounds 1-5 are the first phosphines reported that contain two PTA moieties. All five compounds were characterized by ESI-MS, elemental analysis, ¹H, ¹³C, and ³¹P NMR spectroscopy, while 3 and 4 were additionally analyzed via single crystal X-ray diffraction. The relative positions of the PTA units on the aromatic ring as well as the substituents of the ring had a pronounced effect on the water-solubilities of the systems. The ortho compound (1, 2000 mg/mL) was more than two orders of magnitude more soluble than the para compound (5, 12.5 mg/mL). The meta substituted phenyl (2) and tolyl (3) compounds had solubilities (810 mg/mL) that were more than triple that of PTA (235 mg/mL) while the anisolyl analog (4) was half as soluble (121 mg/mL).     

Synthesis and characterization of cationic rhodium(I) dicarbonyl complexes

Treatment of Rh(acac)(CO)₂ (acac = acetoacetonate) with perchloric acid followed by addition of an α-diimine (α-diimine = 1,4-bis(Ar)-2,3-dimethyl-1,4-diaza-1,3-butadiene, Ar = 3,5-dimethylphenyl, 1; 3,5-di-tert-butylphenyl, 2; and 3,4,5-trimethoxyphenyl, 3; phenyl, 4; and 4-chlorophenyl, 5) generates a series of complexes of the type [Rh(α-diimine)(CO)₂][ClO₄] 6-10 with varying electronic properties of the supporting diimine ligand. X-ray crystal structures have been determined for the α-diimine ligands 1-5, and complexes 6, 8, and 10.     

Imidazolium formation from the reaction of N-heterocyclic carbene stabilised group 13 trihydride complexes with organic acids

The reactions of the N-heterocyclic carbene (NHC) stabilised group 13 trihydride complexes [AlH₃(IMeMe)] (1) (IMeMe = 1,3,4,5-tetramethylimidazol-2-ylidene), [AlH₃(IⁱPrMe)] (2) (IⁱPrMe = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) with three molar equivalents of phenol, and [InH₃(IMes)] (3) (IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazole-2-ylidene) with one molar equivalent of 1,1,1,5,5,5-hexafluoropentan-2,4-dione (F₆acacH) are presented. These render the imidazolium tetraphenoxyaluminate species; [IMeMe · H][Al(OPh)₄] (4) and [IⁱPrMe · H][Al(OPh)₄] (5), and 1,3-bis(2,4,6-trimethylphenyl)imidazolium 1,1,1,5,5,5-hexafluoropentan-2,4-dionate; [IMes · H][CH{C(O)CF₃}₂] (6), the latter leading to metallohydride decomposition. The molecular structures of 4 and 6 are described.     

Novel mononuclear η-pentamethylcyclopentadienyl complexes of platinum group metals bearing pyrazolylpyridazine ligands: Syntheses and spectral studies

Condensation of 3,6-dichloropyridazine with 3,5-dimethylpyrazole in 1:1 ratio yielded one side substituted pyrazolylpyridazine ligand 3-chloro-6-(3,5-dimethylpyrazolyl)pyridazine (L) while condensation of 3,6-dichloropyridazine with substituted pyrazoles in 1:2 ratio yielded both side substituted pyrazolylpyridazine ligands such as 3,6-bis(pyrazolyl)pyridazine (L1), 3,6-bis(3-methylpyrazolyl)pyridazine (L2) and 3,6-bis(3,5-dimethylpyrazolyl)pyridazine (L3). A new series of cationic mononuclear complexes of the type [(η⁵-Cp)M_a(L)(PPh₃)]PF₆, [(η⁵-Cp*)M_b(L)Cl]PF₆, [(η⁵-Cp*)Ru(L′)(PPh₃)]PF₆ and [(η⁵-Cp*)M_b(L′)Cl]⁺ (where M_a = Ru, Os; M_b = Rh, Ir and L′ = L1, L2, L3) bearing pyrazolylpyridazine and η⁵-cyclopentadienyl ligands are reported. The complexes have been completely characterized by spectral studies. The molecular structures of representative complexes have been determined by single crystal X-ray crystallography.     

Preparation and characterization of macrocyclic dinickel complexes coligated by monoalkyl- and dialkylcarbamates

The dinuclear nickel(II) complex [Ni₂L(Cl)]⁺ (1), where (L)²⁻ represents a 24-membered binucleating hexamine-dithiophenolate ligand, reacts readily with primary and secondary amines RR′NH in the presence of CO₂ (1 bar) to give dinuclear monoalkyl- and dialkylcarbamate complexes [Ni₂L(O₂CNRR′)]⁺ (R = H, R′ = CH₂Ph (2), R = H, R′ = n-Bu (3), R = H, R′ = n-Oct (4), R = H, R′ = CH₂CH₂OH (5), R = R′ = Et (6), and R = R′ = CH₂CH₂OH (7)). Complexes 2-7 can also be prepared by the reaction of 1 with CO₂(air)/amine. The carbamate complexes are hydrolyzed in methanolic solution to give the known alkylcarbonate complex [Ni₂L(O₂COMe)]⁺ (8). These conversions are less rapid than the transesterification reactions of 8, due to a less electron-demanding carboxyl C(carbamate) atom. All new complexes were either isolated as perchlorate or tetraphenylborate salts and fully characterized by elemental analysis, UV/Vis, and IR spectroscopy. The structures of 2[BPh₄] and 7[BPh₄] have also been determined by X-ray crystallography. They confirm the presence of μ_1,3-bridging alkylcarbamate units in the products.     

Nickel(II) complexes of terdentate or symmetrical tetradentate Schiff bases: Evidence of the influence of the counter anions in the hydrolysis of the imine bond in Schiff base complexes

Two sets of ligands, set-1 and set-2, have been prepared by mixing 1,3-diaminopentane and carbonyl compounds (2-acetylpyridine or pyridine-2-carboxaldehyde) in 1:1 and 1:2 ratios, respectively, and employed for the synthesis of complexes with Ni(II) perchlorate, Ni(II) thiocyanate and Ni(II) chloride. Ni(II) perchlorate yields the complexes having general formula [NiL₂](ClO₄)₂(L = L¹ [N³-(1-pyridin-2-yl-ethylidene)-pentane-1,3-diamine] for complex 1 or L²[N³-pyridin-2-ylmethylene-pentane-1,3-diamine] for complex 2) in which the Schiff bases are monocondensed terdentate, whereas Ni(II) thiocyanate results in the formation of tetradentate Schiff base complexes, [NiL(SCN)₂] (L = L³[N,N′-bis-(1-pyridin-2-yl-ethylidine)-pentane-1,3-diamine] for complex 3 or L⁴ [N,N′-bis(pyridin-2-ylmethyline)-pentane-1,3-diamine] for complex 4) irrespective of the sets of ligands used. Complexes 5 {[NiL³(N₃)₂]} and 6 {[NiL⁴(N₃)₂]} are prepared by adding sodium azide to the methanol solution of complexes 1 and 2. Addition of Ni(II) chloride to the set-1 or set-2 ligands produces [Ni(pn)₂]Cl₂, 7, as the major product, where pn = 1,3-diaminopentane. Formation of the complexes has been explained by the activation of the imine bond by the counter anion and thereby favouring the hydrolysis of the Schiff base. All the complexes have been characterized by elemental analyses and spectral data. Single crystal X-ray diffraction studies confirm the structures of three representative members, 1, 4 and 7; all of them have distorted octahedral geometry around Ni(II). The bis-complex of terdentate ligands, 1, is the mer isomer, and complexes 4 and 7 possess trans geometry.     

Synthesis and characterization of Ru(arene) complexes of bispyrazolylazines: Catalytic hydrogen transfer of ketones

The bis(pyrazol-1-yl)azine ligands 2,3-bis(pyrazol-1-yl)quinoxaline (bpzqnx), 2,3-bis(pyrazol-1-yl)pyrazine (bpzprz) and 3,6-bis(3,5-dimethylpyrazol-1-yl)pyridazine (bpz*pdz) were prepared by the reaction of pyrazolate salts and the corresponding azine dichloride derivatives. The reaction of these ligands with Ru(arene) precursors led to the mononuclear complexes [RuCl(arene)(L)]BPh₄ (arene = p-cymene, L = bpzqnx, 1, bpzprz, 5, bpz*pdz, 7; arene = C₆H₆, L = bpzqnx, 2, bpzprz, 6, bpz*pdz, 8) with the N-donor ligand coordinated in a bidentate chelate way. In general, the ligands coordinate through one pyrazole ring and the azine, except in the cases of 1 and 2 where the two pyrazolyl rings are coordinated to the metal in a symmetrical way. When the reactions between the ruthenium precursors and bpzqnx are carried out in MeOH, the complexes [RuCl(arene)(OMepzqnx)]BPh₄ with partially methanolyzed ligands are isolated (arene = p-cymene, 3; C₆H₆, 4). In this process a methoxy group has replaced one of the pyrazole groups in the ligand. The X-ray structures of 6 and 7 have been determined. These compounds have a three-legged piano-stool structure with cations and anions packed through weak interactions. Complexes 1-8 are active in ketone hydrogenation transfer processes even in the absence of base.     

Synthesis and structural characterizations of para-bis(dialkyl/diarylphosphino)phenylenes built around tetrahalogenated benzene cores

Double deprotonation of 1,2-dibromo-4,5-difluorobenzene and 1-bromo-2-chloro-4,5-difluorobenzene by lithium diisopropylamide (LDA) in ethereal solutions is facile at very low temperatures (T < −90 °C). The organo-dilithium intermediates thus generated react readily with chlorophosphines ClPR₂ (R = Ph and/or ⁱPr), producing 1,2-dibromo-3,6-bis(diphenylphosphino)-4,5-difluorobenzene (1a), 1,2-dibromo-3,6-bis(diisopropylphosphino)-4,5-difluorobenzene (1b) and 1-bromo-2-chloro-3,6-bis(diphenylphosphino)-4,5-difluorobenzene (1c). Corresponding P-oxides 2a-c are obtained by oxidation of 1a-c with H₂O₂. Analogous reactions of 1,2-dibromo-4,5-difluorobenzene and 1-bromo-2-chloro-4,5-difluorobenzene with only 1 equiv. of LDA do not result in selective monodeprotonations, as 1a and 1c are formed preferentially after ClPPh₂ quench. All of the isolated new compounds were fully characterized by multinuclear NMR spectroscopy, elemental analysis and/or mass-spectrometry. In addition, 1a, 1c, 2a, and 2b were characterized by single crystal X-ray diffraction methods.     

Hybrid scorpionate/cyclopentadienyl titanium and zirconium complexes with alkoxide and imido ligands

The reactivity of hybrid scorpionate/cyclopentadienyl ligand-containing trichloride zirconium complexes [ZrCl₃(bpzcp)] (1) [bpzcp = 2,2-bis(3,5-dimethylpyrazol-1-yl)-1,1-diphenylethylcyclopentadienyl] and [ZrCl₃(bpztcp)] (2) [bpztcp = 2,2-bis(3,5-dimethylpyrazol-1-yl)-1-tert-butylethylcyclopentadienyl] toward several lithium alkoxides has been carried out. Thus, alkoxide-containing complexes [ZrCl₂(OR)(bpzcp)] (R = Me, 3; Et, 4; ⁱPr, 5; (R)-2-Bu, 6), [ZrCl₂(OR)(bpztcp)] (R = Me, 7; Et, 8; ⁱPr, 9; (R)-2-Bu, 10) and [Zr(OR)₃(bpztcp)] (R = Et, 11; ⁱPr, 12) were prepared by deprotonation of the appropriate alcohol group with BuⁿLi followed by reaction with 1 or 2. In addition, the imido-complex [Ti(N^tBu)Cl(bpztcp)(py)] (13) were also prepared. The structures of these complexes have been proposed on basis of spectroscopic and DFT methods.     

Synthesis and characterisation of new N1-alkyl-3,5-dipyridylpyrazole derived ligands. Study of their reactivity with Pd(II) and Pt(II)

Two new pyrazole-derived ligands, 1-ethyl-3,5-bis(2-pyridyl)pyrazole (L¹) and 1-octyl-3,5-bis(2-pyridyl)pyrazole (L²), both containing alkyl groups at position 1 were prepared by reaction between 3,5-bis(2-pyridyl) pyrazole and the appropriate bromoalkane in toluene using sodium ethoxide as base.The reaction between L¹, L² and [MCl₂(CH₃CN)₂] (M = Pd(II), Pt(II)) resulted in the formation complexes of formula [MCl₂(L)] (M = Pd(II), L = L¹ (1); M = Pd(II), L = L² (2); M = Pt(II), L = L¹ (3); M = Pt(II), L = L² (4)). These complexes were characterised by elemental analyses, conductivity measurements, infrared, ¹H, ¹³C{¹H} NMR and HMQC spectroscopies. The X-ray structure of the complex [PtCl₂(L²)] (4) was determined. In this complex, Npyridine and Npyrazole donor atoms coordinate the ligand to the metal, which complete its coordination with two chloro ligands in a cis disposition.     

Synthesis of new platinum(II) complexes containing hybrid thioether-pyrazole ligands: Structural analysis by H and C{H} NMR spectroscopy and X-ray crystal structures

Treatment of the ligands 1,8-bis(3,5-dimethyl-1-pyrazolyl)-3,6-dithiaoctane (bddo), 1,9-bis(3,5-dimethyl-1-pyrazolyl)-3,7-dithianonane (bddn), and 1,6-bis(3,5-dimethyl-1-pyrazolyl)-2,5-dithiahexane (bddh) with several platinum starting materials as K₂PtCl₄, PtCl₂, [PtCl₂(CH₃CN)₂] and [PtCl₂(PhCN)₂] was developed under different conditions. The reactions did not yield pure products. The ratio of the NSSN, NS, SS, NN, and 2NS isomers has been calculated through NMR experiments. Treatment of the mixtures of complexes with NaBPh₄ affords [Pt(NSSN)](BPh₄)₂ (NSSN = bddo, bddn). These Pt(II) complexes have been characterised by elemental analyses, conductivity measurements, IR and ¹H and ¹³C NMR spectroscopy. The X-ray structures of the complexes [Pt(NSSN)](BPh₄)₂ (NSSN = bddo, bddn) have also been determined. In these complexes, the metal atom is tetracoordinated by the two azine nitrogen atoms of the pyrazole rings and two thioether sulfur atoms. When the [Pt(NSSN)](BPh₄)₂ (NSSN = bddo, bddn) complexes were heated under reflux in a solution of Et₄NBr in CH₂Cl₂/CH₃OH (1:1), a mixture of isomers was obtained.     

Oxidative addition of 3,6-di-tert-butyl-o-benzoquinone and 4,6-di-tert-butyl-N-(2,6-di-iso-propylphenyl)-o-iminobenzoquinone to SnCl2

Addition of 3,6-di-tert-butyl-o-benzoquinone (3,6-DBBQ) to SnCl₂ in THF leads to the oxidation of Sn(II) to Sn(IV) with formation of catecholate complex (3,6-DBCat)SnCl₂ · 2THF (1), where 3,6-DBCat is 3,6-di-tert-butyl-catecholate dianion. The reaction of 4,6-di-tert-butyl-N-(2,6-di-iso-propylphenyl)-o-iminobenzoquinone (IBQ-Prⁱ) also proceeds on the oxidative-addition mechanism yielding bis-iminosemiquinonato species (ISQ-Prⁱ)₂SnCl₂(2), where ISQ-Prⁱ is anion-radical 4,6-di-tert-butyl-N-(2,6-di-iso-propylphenyl)-o-iminobenzosemiquinolate. The complexes have been characterized by IR, X-band EPR, ¹H NMR (for 1) spectroscopy and magnetochemistry (for 2). X-ray analysis data show the distorted octahedral environment of tin(IV) for both complexes. Complex 1 is diamagnetic (ground state S = 0), while 2 has triplet ground state (S = 1, biradical). Catecholate complex 1 is able to be a spin trap for different organic radicals.     

The influence of substituents (R) at N atom of thiophene-2-carbaldehyde thiosemicarbazones {(C4H3S)HCN-N(H)-C(S)NHR} on bonding, nuclearity and H-bonded networks of copper(I) complexes

The nuclearity, bonding and H-bonded networks of copper(I) halide complexes with thiophene-2-carbaldehyde thiosemicarbazones {(C₄H₃S)HC²N³-N(H)-C¹(S)N¹HR} are influenced by R substituents at N¹ atom. Thiophene-2-carbaldehyde-N¹-methyl thiosemicarbazone (HttscMe) or thiophene-2-carbaldehyde-N¹-ethyl thiosemicarbazone (HttscEt) have yielded halogen-bridged dinuclear complexes, [Cu₂(μ-X)₂(η¹-S-Htsc)₂(Ph₃P)₂] (Htsc, X: HttscMe, I, 1; Br, 2; Cl, 3; HttscEt, I, 4; Br, 5; Cl, 6), while thiophene-2-carbaldehyde-N¹-phenyl thiosemicarbazone (HttscPh) has yielded mononuclear complexes, [CuX(η¹-S-HttscPh)₂] (X, I, 7a; Br 8; Cl, 9) and a sulfur bridged dinuclear complex, [Cu₂(μ-S-HttscPh)₂(η¹-S-HttscPh)₂I₂] 7b co-existing with 7a in the same unit cell. These results are in contrast to S-bridged dimers [Cu₂(μ-S-Httsc)₂(η¹-Br)₂(Ph₃P)₂] · 2H₂O and [Cu₂(μ-S-Httsc)₂(η¹-Cl)₂(Ph₃P)₂] · 2CH₃CN obtained for R = H and X = Cl, Br (Httsc = thiophene-2-carbaldehyde thiosemicarbazone) as reported earlier. The intermolecular CH_Ph?π interaction in 1-3 (2.797 Å, 1; 3.264 Å, 2; 3.257 Å, 3) have formed linear polymers, whereas the CH_Ph?X and N³?HCH interactions in 4-6 (2.791, 2.69 Å, 5; 2.776, 2.745 Å, 6, respectively) have led to the formation of H-bonded 2D polymer. The PhN¹H?π, interactions (2.547 Å, 8, 2.599 Å, 9) have formed H-bonded dimers only. The Cu?Cu separations are 3.221-3.404 Å (1-6).     

Syntheses and structures of lanthanide complexes containing a bis(imidazolin-2-imino)pyridine pincer ligand

The Lewis acid-base reaction of 2,6-bis[1,3-di-tert-butylimidazolin-2-imino)methyl]pyridine (TL^tBu) and LnCl₃ in THF leads to the corresponding neutral lanthanide complexes of type [(TL^tBu)LnCl₃], Ln = Y (1a), Er (1b), Lu (1c). The yttrium and lutetium complexes have been characterized by X-ray diffraction analysis. The solid state structures reveal that the bulky TL^tBu ligand causes steric crowding around the lanthanide atoms by coordinating to the metal center in a tridentate fashion. In addition, remote C-H?Ln interactions (H?Ln ca. 2.7 Å) involving one of the ^tBu methyl groups are observed in both cases. A DFT (density functional theory) calculation on 1a was able to reproduce this interaction, which was additionally characterized by means of an H?Y compliance constant and by employing the AIM (atoms in molecules) theory.     

Synthesis and high ranked NLT properties of new sulfonamide-substituted indium phthalocyanines

The synthesis and characterization of three new indium phthalocyanines bearing eight N-alkyl- or N-arylsulfonamide groups is described. The new compounds are {2,3,9,10,16,17,23,24-octakis[4-(4-methoxyphenylaminosulfonyl]phenoxy]phthalocyaninato}indium(III) chloride (7), {2,3,9,10,16,17,23,24-octakis[4-diethylaminosulfonyl)phenoxy]phthalocyaninato}indium(III) chloride (8) and {2,3,9,10,16,17,23,24-octakis[4-didodecylaminosulfonyl)phenoxy]phthalocyaninato}indium(III) chloride (9), and were obtained in 23-49% yields. The precursors of phthalocyanines 7-9 are sulfonamide-substituted phthalonitriles that can be prepared by reacting 4,5-bis(4-chlorosulfonylphenoxy)phthalonitrile (3) with amines. The nonlinear transmission (NLT) of complexes 7-9 was determined at 532 nm using ns pulses. All three phthalocyanines behave as reverse saturable absorbers with increasing efficiency of optical limiting in the order 7 < 8 < 9. A comparative analysis of the NLT results is attempted in terms of the structural differences in 7-9.     

Syntheses, crystal structures, and characterization of heteronuclear complexes based on a versatile ligand with both acetylacetonate and bis(2-pyridyl) units

A new type of multidentate ligand with both acetylacetonate and bis(2-pyridyl) units on the 1,3-dithiole moiety, 3-[2-(dipyridin-2-yl-methylene)-5-methylsulfanyl-[1,3]dithiol-4-ylsulfanyl]-pentane-2, 4-dione (L), has been prepared. Through reactions of the ligand with Re(CO)₅X (X = Cl, Br), new rhenium(I) tricarbonyl complexes ClRe(CO)₃(L) (2) and BrRe(CO)₃(L) (3), have been obtained. With the use of 2 or 3 as the precursors, the further reactions with (Tp^Ph2)Co(OAc)(Hpz^Ph2) (Tp^Ph2 = hydrotris(3,5-diphenylpyrazol-1-yl)borate); Hpz^Ph2 = 3,5-diphenyl-pyrazole) or M(OAc)₂(M = Mn, Zn), afford four new heteronuclear complexes: ClRe(CO)₃(L)Co(Tp^Ph2) (4), BrRe(CO)₃(L)Co(Tp^Ph2) (5), [ClRe(CO)₃(L)]₂Mn(CH₃OH)₂ (6) and [ClRe(CO)₃(L)]₂Zn(CH₃OH)₂ (7), respectively. Crystal structures of complexes 2 and 4-7 have been determined by X-ray diffraction. Their absorption spectra, photoluminescence and magnetic properties have been studied.     

Synthesis, spectroscopic properties, X-ray single crystal analysis and antimicrobial activities of organotin(IV) 4-(4-methoxyphenyl)piperazine-1-carbodithioates

A series of mononuclear organotin(IV) complexes of the types, R₃SnL {R = C₄H₉ (1), C₆H₁₁ (2), CH₃ (3) and C₆H₅ (4)}, R₂SnClL {R = C₄H₉ (5), C₂H₅ (7) and CH₃ (9)} and R₂SnL₂ {R = C₄H₉ (6), C₂H₅ (8) and CH₃ (10)}, have been synthesized, where L = 4-(4-methoxyphenyl)piperazine-1-carbodithioate. The ligand-salt and the complexes have been characterized by Raman, FT-IR and multinuclear NMR (¹H, ¹³C and ¹¹⁹Sn) spectroscopy and elemental microanalysis (CHNS). The spectroscopic data substantiate coordination of the ligands to the organotin moieties. The structures of complexes 4 and 6 have been determined by single-crystal X-ray diffraction and illustrate the asymmetric bidentate bonding of the ligand. The packing diagrams indicate O···H and π···H intermolecular interactions in complex 4 and intermolecular S₂C···H interactions in complex 6, resulting in layer structures for both complexes. A subsequent antimicrobial study indicates that the compounds are active biologically and may well be the basis for a new class of fungicides.     

Synthesis, photoluminescence and electrochemiluminescence of ruthenium(II) polypyridyl complexes based on bipyridine derivatives with carbazole moieties

Six complexes (1-6) with the type of [Ru(bpy)₂L]X₂ (1-3: L = L1-L3, X = Cl⁻; 4-6: L = L1-L3, X = PF₆⁻) were synthesized based on 2,2′-bipyridine and three 2,2′-bipyridine derivatives L1, L2 and L3 (L1 = 5,5′-dibromo-2,2′-bipyridine, L2 = 5-bromo-5′-carbazolyl-2,2′-bipyridine, L3 = 5,5′-dicarbazolyl-2,2′-bipyridine). The complexes 1-6 were characterized by ¹H NMR, MS(ESI) and IR spectra, along with the X-ray crystal structure analysis for 1, 5 and 6. Their photophysical properties and electrochemiluminescence (ECL) properties were investigated in detail. In the UV-Vis absorption spectra, all complexes 1-6 show strong intraligand (π → π^∗) transitions and metal-ligand charge transfer (MLCT, dπ (Ru) → π^∗) bands. Upon the excitation wavelengths at ∼508 nm, all complexes 1-6 exhibit typical MLCT emission of ruthenium(II) polypyridyl complexes. The introduction of carbazole moieties improves the MLCT absorption and emission intensity. The ruthenium(II) complexes 1-6 exhibit good electrochemiluminescence (ECL) properties in [Ru(bpy)₂L]²⁺/tri-n-propylamine (TPrA) acetonitrile solution and the complexes with PF₆⁻ showed higher ECL emission intensity than that of the complexes with Cl⁻ based on the same ligands.     

Synthesis and characterization of monomer and dimer complexes of porphyrin iron(III) with bridging phenylcyanamide ligands

Several new mono and dinuclear complexes of [(P)Fe^III(L)], in which P is the dianion of tetraphenylporphyrin(TPP) and tetramesitylporphyrin(TMP) and L is the monoanion of 4-azo(phenylcyanamido)benzene (apc) (1) and (2) or dianion 1,4-di cyanamidobenzene (dicyd) (3), (4), (7), (8) and 4,4′-azo-diphenylcyanamide (adpc) (5), (6), (9), (10) have been prepared by the reaction of [(P)Fe^IIICl] with appropriate thallium salts of phenylcyanamide derivatives. Each of the complexes has been characterized by FT-IR, UV-Vis, ¹H NMR, MALDI-TOF and EPR spectroscopic data. In non-coordinating solvents (such as toluene or chloroform) these complexes exhibit ¹H NMR spectra that are characteristic of high-spin (S = 5/2) species. The cyanamide group (NCN) of the bridging ligand is coordinated to Fe(III) ions through the nitrile-nitrogen. The iron(III) phenylcyanamide complexes are not reactive toward dioxygen, they convert into [TPPFe^IIICl] when treated with HCl. EPR and NMR have shown that in dinuclear complexes weak magnetic interactions take place between two iron(III) paramagnetic centers.     

Palladium(II) complexes obtained from 3,4-bis(cyanamido)cyclobutane-1,2-dione dianion

Three palladium(II) complexes have been synthesized, using 3,4-bis(cyanamido) cyclobutane-1,2-dione dianion (3,4-bis(cyanamido)squarate or 3,4-NCNsq²⁻): [Pd(en)(3,4-NCNsq)] · 1.5H₂O (1) (en=1,2-diaminoethane), [Pd(en)(3,4-(NC(O)NH₂)sq)] · 0.5H₂O (2) and K₃Na[Pd₂(3,4-(NCN)₂sq)₄] · 5H₂O (3). Complex 1 has been characterized by elemental analysis, IR and ¹³C NMR spectroscopies. Complexes 2 and 3 have been characterized by single-crystal X-ray diffraction. In complex 2, the unusual hydration of the cyanamido ligand was observed, it proceeds in the coordination sphere of the palladium and leads to a chelating urea squarate ligand. Complex 3 is an anionic dinuclear complex containing four bridging cyanamido squarate ligands. In complexes 2 and 3, the 3,4-NCNsq²⁻ ligand (hydrated or not) is, for the first time, coordinated to the metal atom by the two amido nitrogen atoms, either in a chelating mode (complex 2) or in a bridging mode giving a short Pd ? Pd distance of 2.8866(15) Å (complex 3). Electrochemical studies in acetonitrile and dmf solutions have been performed on complexes 1 and 3.