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Two novel supramolecular heteroleptic complexes [Pb2L2(NO3)2]n (1) and {[Pb3L3](ClO4)3}n·3.25nH2O (2·3.25nH2O), obtained from N′-(piperidine-1-carbonothioyl)picolinohydrazonamide (HL) and Pb(NO3)2 or Pb(ClO4)2 in aqueous methanol are reported. A crucial role of the auxiliary ligand (NO3−vs. ClO4−) was revealed as a driving force for the formation of the resulting architecture of complexes, which, in turn, are dictated by the formation of tetrel bonds. Complex 1 is constructed from heteroleptic dinuclear centrosymmetric species [Pb2L2(NO3)2], which, in turn, are formed from the heteroleptic mononuclear symmetry related [PbL(NO3)] units, linked through a pair of bonds formed between the metal cations and the thioamide nitrogen atoms. The metal cations form a weaker tetrel bond with the symmetry related nitrate atoms, yielding a 1D polymeric chain structure. These chains are interlinked through N–H⋯O hydrogen bonds, formed between the covalently coordinated nitrate oxygen atom and the NH2 hydrogen atom, yielding a 2D supramolecular architecture. Complex 2·3.25nH2O is constructed from the trinuclear species [Pb3L3](ClO4)3. The trinuclear cation is constructed from three [PbL]+ cations interlinked through two Pb–S and two Pb–N bonds, formed with the thiocarbonyl sulfur atoms and the amide nitrogen atoms. The cations [Pb3L3]3+ are interlinked through two Pb–N and two Pb–S bonds yielding a 1D supramolecular polymeric cationic chain {[Pb3L3]3+}n. The two metal cations corresponding to two [PbL]+ units, linked through a pair of the Pb–S bonds, are additionally bridged by two oxygen atoms of one of the perchlorate anions with the formation of two Pb⋯O tetrel bonds. The coordination spheres of the metal cations are filled by one of the oxygen atoms of two different perchlorate anions with the formation of tetrel bonds. One of these perchlorates also forms the N–H⋯O hydrogen bond within the trinuclear unit [Pb3L3](ClO4)3. 1D supramolecular chains {[Pb3L3]3+}n are interlinked through a myriad of hydrogen bonds formed by the perchlorate anions and crystallized water molecules. The tetrel bonds involving the counterions (Pb⋯O) have been also analysed by DFT calculations via a MEP surface plot and 2D maps of electron localization function (ELF), Laplacian of electron density (∇2ρ) and reduced density gradient (RDG), confirming their noncovalent nature. [ABSTRACT FROM AUTHOR]

In this contribution, a novel binuclear heteroleptic complex [Pb2L2(CO3)]·2CH3CN·2MeOH (1·2CH3CN·2MeOH) is reported, which was fabricated by electrochemical oxidation of a lead anode under an ambient atmosphere in a CH3CN : MeOH solution of N′-isonicotinoylpyrazine-2-carbohydrazonamide (HL). The CO32− anion was produced from the conversion of aerial CO2 by the Pb2+–L complex system under electrochemical conditions. In the structure of 1, ligand L exhibits a tridentate pincer-like N,N′,O-coordination mode, while the CO32− anion exhibits a tetradentate bridging coordination mode with one of the oxygen atoms exhibiting a bridging μ-coordination mode. The metal cations in the structure of 1 are in a five-membered N2O3 coordination environment, formed by covalent bonds. The molecular structure of 1·2CH3CN·2MeOH is stabilized by a pair of intermolecular Pb⋯N tetrel bonds formed with one of the NH2 nitrogen atoms of an adjacent complex molecule and with the acetonitrile nitrogen atom, and one Pb⋯O tetrel bond formed with the carbonyl oxygen atom of the other adjacent complex molecule, yielding a 2D supramolecular sheet. This sheet is further stabilized by intermolecular N–H⋯Nacetonitrile and N–H⋯Ocarbonate hydrogen bonds and πPyrazine⋯πPyridine interactions. The optical properties of the complex were revealed by UV-vis spectroscopy and spectrofluorimetry in MeOH. It was established that the described complex is emissive upon excitation at 340 nm with a broad band from about 500 nm to 780 nm with a maximum at ∼580 nm, accompanied by a shoulder at ∼620 nm. The CIE-1931 chromaticity coordinates of (0.28, 0.36) fall within the white gamut of the chromaticity diagram. Thus, complex 1 is a single-component white light-emitting phosphor. [ABSTRACT FROM AUTHOR]

Three new PbII complexes [Pb(LI)(SCN)]n, {[Pb(LII)](SCN)}n and {[Pb(HLIII)(SCN)](SCN)}n (HLI = N′-phenyl(pyridin-2-yl)methylene-N-phenylthiosemicarbazide, HLII = N′-amino(pyrazin-2-yl)methylenethiosemicarbazide, HLIII = N′-amino(pyridin-2-yl)methylenethiosemicarbazide) have been synthesized and characterized by spectroscopic techniques and single crystal X-ray diffraction. In all complexes, the corresponding organic ligand behaves as a tridentate N,N′,S-chelating species. A 1D supramolecular polymeric aggregation in complex [Pb(LI)(SCN)]n is dictated by the Pb⋯NCS and Pb⋯S＝C tetrel bonds formed between the [Pb(LI)(SCN)] species. 1D cationic coordination polymers ([Pb(LII)])nn+ in the structure of complex {[Pb(LII)](SCN)}n are linked into a 2D supramolecular polymeric layer through the Pb⋯NCS tetrel bonds and Pb⋯π(NCS) interactions formed with the nitrogen atom and the conjugated system of the free SCN− anions, respectively. The cationic species [Pb(HLIII)(SCN)]+ in the structure of complex {[Pb(HLIII)(SCN)](SCN)}n produce a 1D supramolecular polymer due to the Pb⋯SCN and Pb⋯S＝C tetrel bonds, further stabilized by the Pb⋯π(NCS) interactions formed with the conjugated system of the coordinated NCS− anion. The latter anions also link these 1D chains through the Pb⋯SCN tetrel bonds, yielding 1D supramolecular polymeric ribbons. The energetic relevance of the Pb⋯S and Pb⋯N tetrel bonds has been studied by DFT calculations. The tetrel bonds have been characterized using QTAIM and NCIplot analysis and rationalized using molecular electrostatic potential surface calculations. [ABSTRACT FROM AUTHOR]

We report a heteroleptic complex [PbCl2(HL′)]·MeOH (1·MeOH), obtained from N′-isonicotinoylpicolinohydrazonamide (HL) and PbCl2, where HL′ is a zwitterionic form of HL with the protonated 4-pyridyl and deprotonated amide nitrogen atoms. All the coordination bonds around the Pb2+ cation are collected in one hemisphere, yielding a large space gap, which allows two molecules of 1 to come into close proximity to each other and linked through two Pb⋯Cl tetrel bonds of ∼3.41 Å. As a result, a supramolecular dimeric species [PbCl2(HL′)]2 is formed, which is stabilized by two C–H⋯Pb anagostic and two C–H⋯Cl interactions. The coordination sphere of the Pb2+ cation is completed by the formation of the Pb⋯O tetrel bond with the methanolic oxygen atom. The supramolecular dimeric species are linked through π⋯π(chelate ring) and π⋯π interactions, yielding a 1D supramolecular chain, which is strengthened by N–H⋯Cl hydrogen bonds. These chains are interlinked through a set of hydrogen bonds and weaker interactions. Extensive computational analyses by charge and energy decomposition scheme ETS-NOCV as well as interacting quantum atoms (IQA) allowed us to conclude that most electrostatically dominated noncovalent interactions follow the strength order: Pb⋯O > Pb⋯Cl > N–H⋯Cl > C–H⋯Pb > C–H⋯Cl. Cooperative action of π⋯π and N–H⋯Cl provides an extraordinary dimeric stabilization energy of about −75 kcal mol−1. Finally, an unusual C–H⋯Pb interaction was identified to be attractive despite its long distance (>3.7 Å). Methanol species is found to be engaged not only in Pb⋯O tetrel bonds, but also in hydrogen N–H⋯O bonds and untypical homopolar dihydrogen interactions C–H⋯H–C. [ABSTRACT FROM AUTHOR]

New nickel and copper bisdithiolene complexes were prepared as tetraphenylphosphonium (Ph4P+) salts, (Ph4P)n[M(3cbdt)2], [n = 1, 2; M = Ni, Cu; 3cbdt = 3-cyanobenzene-1,2-dithiolate]: (Ph4P)2[Ni(3cbdt)2] (1); Ph4P[Ni(3cbdt)2] (2); (Ph4P)2[Cu(3cbdt)2] (3); Ph4P[Cu(3cbdt)2] (4), and characterised by single crystal X-ray diffraction, cyclic voltammetry, EPR and static magnetic susceptibility for the paramagnetic species. These Cu and Ni complexes obtained as stable monoanionic and dianionic anions are the first members of this family of cyano benzene functionalized bisdithiolene transition metal complexes, opening the way to the preparation of analogous compounds with other transition metals and their future use as building blocks for the preparation of molecular materials. Their properties are discussed in comparison with the corresponding complexes based on the 4-cyanobenzene-1,2-dithiolate (4cbdt) ligand previously described by us. The salts (Ph4P)n[M(3cbdt)2], [n = 1, 2; M = Ni, Cu] present the metal complexes always in a square-planar coordination geometry with a ligand trans configuration, but revealing a rich polymorphism. The Ni and Cu compounds are isostructural and occur as two polymorphs (α, β) with the exception of the salt of the monoanionic Ni complex, that was found only as the α-polymorph. The salt of the dianionic Ni complex was found to crystallise also with one acetonitrile molecule, when recrystallised from this solvent. The salts of monoanionic [Ni(3cbdt)2] and dianionic [Cu(3cbdt)2] complexes have been characterised by EPR and static magnetic susceptibility as paramagnetic S = 1/2 species. [ABSTRACT FROM AUTHOR]

The family of recently described salts based on the electron donor CNB-EDT-TTF (5-cyanobenzene-ethylenedithio-tetrathiafulvalene) and different anions A, with general formula (CNB-EDT-TTF)4A, constitutes an unprecedented type of molecular conductor based on a bilayer structure of the donors. The crystal structures of the bilayer conductors (CNB-EDT-TTF)4A with small discrete anions are reviewed and analyzed considering previously reported compounds with different anions (A = I3−, ClO4−, BF4−, ReO4−, PF6− and SbF6−), as well as three new members of this family described here with AsF6−, AuI2−and I2Br−. A common structural feature of this family of compounds is the head-to-head arrangement of the donors, induced by a network of weak C≡N⋯H–C interactions, which can be described as an effective combination of R 22 (10) and R 24 (10) synthons, forming donor bilayers alternating with anionic layers. The magnitude of the interactions associated with R 22 (10) and R 24 (10) synthons is estimated to be 4.7 and 10.0 kcal mol−1, respectively. In spite of the common donor bilayer arrangement, a rich diversity of structural variations and polymorphs is observed. These structures are related to different types of donor or anion arrangements, which are analyzed. For all anions a β′′-type packing pattern of the donor molecules arranged in virtually identical bilayers is observed. However, for (CNB-EDT-TTF)4I3, so far a unique exception in this family of compounds, a distinct κ-type packing of the donors, is also obtained as a metastable phase as shown also by DFT calculations that predict the κ-phase above the β′′-phase. Another type of polymorphism is observed in β′′-(CNB-EDT-TTF)4A, compounds with tetrahedral anions, related to the tilting of the donor molecules (either alternating or uniform) in successive bilayers, leading to monoclinic or triclinic unit cells, with doubling of one cell parameter corresponding to the thickness of one bilayer (∼25 Å). Finally, the anions, which often appear with fractional site occupation factors, can be ordered in the anionic plane, with different degrees of correlation between successive anion planes as shown in the AsF6.compound. The implications of these structural features in the electronic properties of these compounds are also discussed. [ABSTRACT FROM AUTHOR]

We report the relevance of cation–anion and cation–solvent–anion interactions to the crystal lattice rigidity and the corresponding effect on the SCO behaviour of six FeIII complexes with the hexadentate Schiff base ligand nsal2trien. Four of these compounds were synthesized and structurally and magnetically characterized for the first time. In the most rigid structures, the SCO behaviour is either not allowed or severely hampered. For lower structural connectivity, incomplete transitions are observed within the 4–300 K temperature range. The most flexible structure shows a complete transition. The interactions between the cationic units and the anions were found to be more important than the cation–cation interactions for the SCO phenomenon and for the overall cooperativity related to the abrupt/gradual character of the transition. Computational studies were performed in order to determine the crystal splitting gap Δoct. The calculated values for the HS and LS Δoct are very similar for all compounds suggesting that these parameters have very little influence on the SCO behaviour. [ABSTRACT FROM AUTHOR]

The reaction of 2-cyanopyridine or 2-cyanopyrazine with N-methylthiosemicarbazide afforded (Z)-2-(amino(pyridin-2-yl)methylene)-N-methylhydrazinecarbothioamide (HPyAm4M) and (Z)-2-(amino(pyrazin-2-yl)methylene)-N-methylhydrazinecarbothioamide (HPzAm4M), respectively. Prolonged heating under reflux in methanol in the synthesis of these thiosemicarbazones led to the formation of 4-methyl-5-pyridin-2-yl-2,4-dihydro-[1,2,4]triazole-5-thione (HMPytat, 1) and 4-methyl-5-pyrazin-2-yl-2,4-dihydro-[1,2,4]triazole-5-thione (HMPztat, 2) by oxidative cyclization of the starting thiosemicarbazones. Reactions of thiosemicarbazones with mercury(ii) salts gave new complexes of general formulae [Hg(tat)X] (3, 4) and [Hg(Htat)2X2] (5, 7, 9–11), along with [Hg3(HEPytat)2(EPytat)2Cl4]·3H2O (6) and [Hg(EPytat)(HEPytat)I]·H2O (8) (Htat = general 1,2,4,-triazole-5-thione). The complexes were isolated as solids and were characterized by elemental analysis, mass spectrometry and IR, 1H NMR and 13C NMR spectroscopy. Recrystallization of the complexes from DMSO gave the compounds [Hg(MPytat)2]n (3a), [Hg(HMPytat)2Br2]·H2O (4a), [{Hg(HEPytat)(μ2-NS-EPytat)Cl2}2Hg] (6a), [Hg(EPytat)2]n (6b), [Hg(MPztat)2]n (10a) and [Hg(EPztat)2]n (11a) (HEPytat = 4-ethyl-5-pyridin-2-yl-2,4-dihydro-[1,2,4]triazole-5-thione and HEPztat = 4-ethyl-5-pyrazin-2-yl-2,4-dihydro-[1,2,4]triazole-5-thione). These complexes were studied by single-crystal X-ray diffraction. The structural analysis revealed the versatility of heterocyclic functionalized 1,2,4-triazole-5-thiones to coordinate to mercury(ii) in the thione and thiolate forms through the use of various donor atoms to give different and interesting crystalline packings. The supramolecular assemblies observed in the solid state were analysed. These elegant assemblies are formed by a combination of several noncovalent interactions, including intermolecular hydrogen-bonding supramolecular synthons and aromatic–aromatic interactions. The short Hg…Hg distance of 3.660 Å indicates the presence of a probable mercurophilic interaction in 6a. [ABSTRACT FROM AUTHOR]

The crystal structure of the new (BrBzPy)2[Fe(qdt)2]2complex (qdt = quinoxalinedithiolate) shows a rare weak FeIIIbisdithiolene dimerisation with unusual molecular planarity and long apical S–Fe distances. This anion configuration is intermediate between the only monomeric Fe bisdithiolene reported so far, with isolated square planar [Fe(qdt)2]−units, and the common strong dimeric geometry also observed in other [Fe(qdt)2]2salts. The standard strong dimeric situation is also observed in the [Fe(α-tpdt)2]2salt (α-tpdt = 2,3-thiophenedithiolate) with the same cation, as well as with n-Bu4N and Et4N showing the influence of different ligands and cations on the coordination geometry and supramolecular structure of the FeIIIcomplexes. [ABSTRACT FROM AUTHOR]

The reaction of 2-cyanopyridine or 2-cyanopyrazine with N-methylthiosemicarbazide afforded (Z)-2-(amino(pyridin-2-yl)methylene)-N-methylhydrazinecarbothioamide (HPyAm4M) and (Z)-2-(amino(pyrazin-2-yl)methylene)-N-methylhydrazinecarbothioamide (HPzAm4M), respectively. Prolonged heating under reflux in methanol in the synthesis of these thiosemicarbazones led to the formation of 4-methyl-5-pyridin-2-yl-2,4-dihydro-[1,2,4]triazole-5-thione (HMPytat, 1) and 4-methyl-5-pyrazin-2-yl-2,4-dihydro-[1,2,4]triazole-5-thione (HMPztat, 2) by oxidative cyclization of the starting thiosemicarbazones. Reactions of thiosemicarbazones with mercury(ii) salts gave new complexes of general formulae [Hg(tat)X] (3, 4) and [Hg(Htat)2X2] (5, 7, 9–11), along with [Hg3(HEPytat)2(EPytat)2Cl4]·3H2O (6) and [Hg(EPytat)(HEPytat)I]·H2O (8) (Htat = general 1,2,4,-triazole-5-thione). The complexes were isolated as solids and were characterized by elemental analysis, mass spectrometry and IR, 1H NMR and 13C NMR spectroscopy. Recrystallization of the complexes from DMSO gave the compounds [Hg(MPytat)2]n (3a), [Hg(HMPytat)2Br2]·H2O (4a), [{Hg(HEPytat)(μ2-NS-EPytat)Cl2}2Hg] (6a), [Hg(EPytat)2]n (6b), [Hg(MPztat)2]n (10a) and [Hg(EPztat)2]n (11a) (HEPytat = 4-ethyl-5-pyridin-2-yl-2,4-dihydro-[1,2,4]triazole-5-thione and HEPztat = 4-ethyl-5-pyrazin-2-yl-2,4-dihydro-[1,2,4]triazole-5-thione). These complexes were studied by single-crystal X-ray diffraction. The structural analysis revealed the versatility of heterocyclic functionalized 1,2,4-triazole-5-thiones to coordinate to mercury(ii) in the thione and thiolate forms through the use of various donor atoms to give different and interesting crystalline packings. The supramolecular assemblies observed in the solid state were analysed. These elegant assemblies are formed by a combination of several noncovalent interactions, including intermolecular hydrogen-bonding supramolecular synthons and aromatic–aromatic interactions. The short Hg…Hg distance of 3.660 Å indicates the presence of a probable mercurophilic interaction in 6a. [ABSTRACT FROM AUTHOR]