Host–guest supramolecular polymers constructed of aniline derivatives and three-dimensional coordination polymers [(n-Bu3Sn)2(R3Sn)Fe(CN)6] n,R = n-Bu or Ph

The straightforward self-assembly reaction of R₃Sn⁺ and [Fe(CN)₆]^3? affords three-dimensional (3-D) coordination polymers [(n-Bu₃Sn)₂(R₃Sn)Fe(CN)₆] _n , R = n-Bu(I) or Ph(II). The architecture of these coordination polymers is closely related to zeolite and acts as a host with wide internal cavities or channels capable of encapsulating voluminous organic compounds. Aniline derivatives acting as guest are encapsulated within the cavities of the 3-D-polymeric hosts I and II by tribochemical reaction producing host–guest supramolecular polymers. The structures and physical properties of these hosts and their host–guest systems were investigated by elemental analysis, X-ray powder diffraction, IR, UV-vis, EPR, and magnetic measurements. The morphology of these systems was examined by scanning electron microscopy (SEM). The interesting feature of these host–guest supramolecular polymers is the enhanced electrical conductivities over those of the 3-D-coordination polymeric hosts upon encapsulation of conductive polymers within their cavities.     

Gadolinium(III)‐Hydroxy Ladders Trapped in Succinate Frameworks with Optimized Magnetocaloric Effect

Two kinds of inorganic gadolinium(III)‐hydroxy “ladders”, [2×n] and [3×n], were successfully trapped in succinate (suc) coordination polymers, [Gd₂(OH)₂(suc)₂(H₂O)]_n ? 2n H₂O ( 1 ) and [Gd₆(OH)₈(suc)₅(H₂O)₂]_n ? 4n H₂O ( 2 ), respectively. Such coordination polymers could be regarded as alternating inorganic–organic hybrid materials with relatively high density. Magnetic and heat capacity studies reveal a large cryogenic magnetocaloric effect (MCE) in both compounds, namely (ΔH=70 kG) 42.8 J kg^?1 K^?1 for complex 1 and 48.0 J kg^?1 K^?1 for complex 2 . The effect of the high density is evident, which gives very large volumetric MCEs up to 120 and 144 mJ cm^?3 K^?1 for complexes 1 and 2 , respectively.     

Poly(DCAQI): Synthesis and characterization of a new redox‐active polymer

Redox‐active anthraquinone based polymers are synthesized by the introduction of a polymerizable vinyl and ethynyl group, respectively, resulting in redox‐active monomers, which electrochemical behaviors are tailored by the modification of the keto groups to N‐cyanoimine moieties. These monomers can be polymerized by free radical polymerization and Rh‐catalyzed polymerization methods, respectively. The resulting polymers are obtained in molar masses (M_n) of 4,400 to 16,800 g mol^?1 as well as high yields of up to 97%. The monomers and polymers are furthermore electrochemically characterized by cyclic voltammetry. The monomers exhibit two one‐electron redox reactions at about ?0.6 and ?1.0 V versus Fc⁺/Fc. The N‐cyanoimine units are, however, partially hydrolyzed during the polymerization step or during the electrochemical measurements and degenerate to carbonyl groups, resulting in a new reduction signal at ?1.26 V versus Fc⁺/Fc. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1998–2003     

Rhodium‐ and ruthenium‐complex‐catalyzed condensation of ferrocene‐containing dithiols and diols with diarylsilanes to give silaferrocenophanes and ferrocene polymers

1,1′‐Ferrocenedithiol reacts with di(4‐methoxyphenyl)silane, diphenylsilane, and di(4‐fluorophenyl)silane in the presence of RhCl(PPh₃)₃ catalyst to give mixtures of 2,2‐diaryl‐1,3‐dithia‐2‐sila[3]ferrocenophanes (1a–3a) and ? (Fc? S? SiAr₂? S) _n? (Fc = 1,1′‐ferrocenylene; 1b: Ar = C₆H₄OMe‐4; 2b: Ar = Ph; 3b: Ar = C₆H₄F‐4). The products are isolated and characterized by NMR spectroscopy and elemental analyses. The polymers 1b–3b, obtained from a toluene‐soluble fraction of the products, show GPC elution patterns corresponding to M_n values of 2700–4600 (polystyrene standards). The UV–vis spectra of the ferrocenophanes and polymers exhibit a d–d transition peak at about 440 nm, while the polymers show a π–π* transition peak at 320–330 nm. The cyclic voltammograms of 3a (Ar = C₆H₄F ? 4) and 3b show a reversible redox of the iron center at 0.27 V and 0.35 V (Ag⁺/Ag) respectively. Reaction of 1,1′‐ferrocenedimethanol with diphenylsilane in the presence of RuCl₂(PPh₃)₃ catalyst results in selective formation of 3,3‐diphenyl‐2,4‐dioxa‐3‐sila[5]ferrocenophane ( 4 ), whose structure was determined by X‐ray crystallography. Copyright © 2001 John Wiley & Sons, Ltd.     

Rapid cooling experiments and use of an anionic nuclear probe to sense the spin transition of the 1D coordination polymers [Fe(NH2trz)3]SnF6n x H2O (NH2trz=4-amino-1,2,4-triazole)

[Fe(NH₂trz)₃]SnF₆ ? n H₂O (NH₂trz=4‐amino‐1,2,4‐triazole; n=1 ( 1 ), n=0.5 ( 2 )) are new 1D spin‐crossover coordination polymers. Compound 2 exhibits an incomplete spin transition centred at around 210 K with a thermal hysteresis loop approximately 16 K wide. The spin transition of 2 was detected by the Mössbauer resonance of the ¹¹⁹Sn atom in the SnF₆^2? anion primarily on the basis of the evolution of its local distortion. Rapid‐cooling ⁵⁷Fe Mössbauer and superconducting quantum interference device experiments allow dramatic widening of the hysteresis width of 2 from 16 K up to 82 K and also shift the spin‐transition curve into the room temperature region. This unusual behaviour of quenched samples on warming is attributed to activation of the molecular motion of the anions from a frozen distorted form towards a regular form at temperatures well above approximately 210 K. Potential applications of this new family of materials are discussed.     

[Fe(TPT)2/3{MI(CN)2}2]⋅nSolv (MI=Ag,Au): New Bimetallic Porous Coordination Polymers with Spin‐Crossover Properties

Two new heterobimetallic porous coordination polymers with the formula [Fe(TPT)_2/3{M^I(CN)₂}₂] ? nSolv (TPT=[(2,4,6‐tris(4‐pyridyl)‐1,3,5‐triazine]; M^I=Ag (nSolv=0, 1 MeOH, 2 CH₂Cl₂), Au (nSolv=0, 2 CH₂Cl₂)) have been synthesized and their crystal structures were determined at 120 K and 293 K by single‐crystal X‐ray analysis. These structures crystallized in the trigonal R‐3m space group. The Fe^II ion resides at an inversion centre that defines a [FeN₆] coordination core. Four dicyanometallate groups coordinate at the equatorial positions, whilst the axial positions are occupied by the TPT ligand. Each TPT ligand is centred in a ternary axis and bridges three crystallographically equivalent Fe^II ions, whilst each dicyanometallate group bridges two crystallographically equivalent Fe^II ions that define a 3D network with the topology of NbO. There are two such networks, which interpenetrate each other, thereby giving rise to large spaces in which very labile solvent molecules are included (CH₂Cl₂ or MeOH). Crystallographic analysis confirmed the reversible structural changes that were associated with the occurrence of spin‐crossover behaviour at the Fe^II ions, the most significant structural variation being the change in unit‐cell volume (about 59 ų per Fe^II ion). The spin‐crossover behaviour has been monitored by means of thermal dependence of the magnetic properties, Mössbauer spectroscopy, and calorimetry.     

(4,4′‐Bipyridine)mercury(II) Coordination Polymers,Syntheses, and Structures

Mercury(II) complexes with 4,4′‐bipyridine (4,4′‐bipy) ligand were synthesized and characterized by elemental analysis, and IR, ¹H‐ and ¹³C‐NMR spectroscopy. The structures of the complexes [Hg₃(4,4′‐bipy)₂(CH₃COO)₂(SCN)₄]_n ( 1 ), [Hg₅(4,4′‐bipy)₅(SCN)₁₀]_n ( 2 ), [Hg₂(4,4′‐bipy)₂(CH₃COO)₂]_n(ClO₄)_2n ( 3 ), and [Hg(4,4′‐bipy)I₂]_n ( 4 ) were determined by X‐ray crystallography. The single‐crystal X‐ray data show that 2 and 4 are one‐dimensional zigzag polymers with four‐coordinate Hg‐atoms, whereas 1 is a one‐dimensional helical chain with two four‐coordinate and one six‐coordinate Hg‐atom. Complex 3 is a two‐dimensional polymer with a five‐coordinate Hg‐atom. These results show the capacity of the Hg‐ion to act as a soft acid that is capable to form compounds with coordination numbers four, five, and six and consequently to produce different forms of coordination polymers, containing one‐ and two‐dimensional networks.     

Star poly(methyl methacrylate) with end‐functionalized arm chains by ruthenium‐catalyzed living radical polymerization

Star polymers with end‐functionalized arm chains (surface‐functionalized star polymers) were synthesized by the in situ linking reaction between ethylene glycol dimethacrylate (linking agent) and an α‐end‐functionalized linear living poly(methyl methacrylate) in RuCl₂(PPh₃)₃‐catalyzed living radical polymerization; the terminal on the surface functionalities included amides, alcohols, amines, and esters. The star polymers were obtained in high yields (75–90%) with initiating systems consisting of a functionalized 2‐chloro‐2‐phenylacetate or ‐acetamide [F? C(O)CHPhCl; F = nPrNH? , HOCH₂CH₂O? , Me₂NCH₂CH₂O? , or EtO? ; initiator] and n‐Bu₃N (additive). The yield was lower with a functionalized 2‐bromoisobutyrate [Me₂NCH₂CH₂OC(O)CMe₂Br] initiator or with Al(Oi‐Pr)₃ as an additive. Multi‐angle laser light scattering analysis showed that the star polymers had arm numbers of 10–100, radii of gyration of 6–23 nm, and weight‐average molecular weights of 1.3 × 10⁵ to 3.0 × 10⁶, which could be controlled by the molar ratio of the linking agent to the linear living polymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1972–1982, 2002     

Photocontrolled Ring‐Opening Polymerization of Strained Dicarba[2]Ferrocenophanes: A Route to Well‐Defined Polyferrocenylethylene Homopolymers and Block Copolymers

The ring‐opening polymerization (ROP) behavior of a variety of substituted 1,1′‐ethylenylferrocenes, or dicarba[2]ferrocenophanes, is reported. The electronic absorption spectra and tilted solid‐state structures of the monomers rac‐[Fe(η⁵‐C₅H₄)₂(CHiPr)₂] ( 7 ), [Fe(η⁵‐C₅H₄)₂(C(H)MeCH₂)] ( 8 ), and rac‐[Fe(η⁵‐C₅H₄)₂(CHPh)₂] ( 9 ) are consistent with the presence of substantial ring strain, which was exploited to synthesize soluble, well‐defined polyferrocenylethylenes (PFEs) [Fe(η⁵‐C₅H₄)₂(C(H)MeCH₂)]_n ( 12 ) and [Fe(η⁵‐C₅H₄)₂(CHPh)₂]_n ( 13 ) through photocontrolled ROP. Polymer chain lengths could be controlled by the monomer‐to‐initiator ratio up to about 50 repeat units and, consistent with the “living” nature of the polymerizations, sequential block copolymerization with a sila[1]ferrocenophane led to polyferrocenylethylene–polyferrocenylsilane (PFE‐b‐PFS) block copolymers ( 14 and 15 ). PFE polymers 12 and 13 showed two reversible oxidation waves, indicative of appreciable Fe???Fe interactions along the polymer backbone. The diblock copolymers were characterized by NMR spectroscopy, GPC analysis, and cyclic voltammetry.     

Nanostructured polymetallaynes of controlled length: Synthesis and characterization of oligomers and polymers from 1,1′‐bis‐(ethynyl)4,4′‐biphenyl bridging Pt(II) or Pd(II) centers

The reactivity of square planar palladium(II) and platinum(II) complexes in trans or cis configuration, namely trans or cis‐[dichlorobis(tributylphosphine)platinum(II)] and trans‐[dichlorobis(tributylphosphine)palladium(II)] with 1,1′‐bis(ethynyl) 4,4′‐biphenyl, DEBP, leading to π‐conjugated organometallic oligomeric and polymeric metallaynes, was investigated by a systematic variation of the reaction conditions. The formation of polymers and oligomers with defined chain length [? M(PBu₃)₂ (C?C? C₆H₄? C₆H₄? C?C? )]_n (n = 3–10 for the oligomers, n = 20–50 for the polymers) depends on the configuration of the precursor Pt(II) and Pd(II) complexes, the presence/absence of the catalyst CuI, and the reaction time. A series of model reactions monitored by XPS, GPC, and NMR ³¹P spectroscopy showed the route to modulate the chain growth. As expected, the nature of the transition metal (Pt or Pd) and the molecular weight of the polymers markedly influence the photophysical characteristics of the polymetallaynes, such as optical absorption and emission behavior. Polymetallaynes with nanostructured morphology could be obtained by a simple casting procedure of polymer solutions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3311–3329, 2007     

Pendant structure governed anion sensing property for sulfonamide‐functionalized poly(phenylacetylene)s bearing various α‐amino acids

The colorimetric detection of anionic species has been studied for α‐amino acid‐conjugated poly(phenylacetylene)s, which were prepared by the polymerization of the ethyl esters of N‐(4‐ethynylphenylsulfonyl)‐L ‐alanine, L ‐isoleucine, L ‐valine, L ‐phenylalanine, L ‐aspartic acid, and L ‐glutamic acid using Rh⁺(2,5‐norbornadiene)[(η⁶‐C₆H₅)B^?(C₆H₅)₃] as the catalyst in CHCl₃. The one‐handed helical conformations of all the sulfonamide‐functionalized polymers were characterized by Cotton effects in the circular dichroism spectra. The addition of anions with a relatively high basicity, such as tetra‐n‐butylammonium acetate and fluoride, induced drastic changes in both the optical and chiroptical properties. On the other hand, anions with a relatively low basicity, such as tetra‐n‐butylammonium nitrate, azide, and bromide, had essentially no effects on the helical conformation of all the sulfonamide‐functionalized polymers. The anion signaling property of the sulfonamide‐functionalized polymers possessing α‐amino acid moieties was significantly affected by the installed residual amino acid structures. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1683–1689, 2010     

Molecular and Crystal Structures of Mononuclear trans‐[Fe(CN)2(tOcNC)4] and trans‐[Mn(CN)(CO)(tOcNC)4] as well as of Cyanide Bridged Coordination Polymers Derived from trans‐[M(CN)2(tOcNC)4] (M = Fe,Ru)

The octahedral complexes trans‐[Fe(CN)₂(^tOcNC)₄] and trans‐[Mn(CN)(CO)(^tOcNC)₄] are produced by the reaction of 2‐isocyano‐2,4,4‐trimethyl‐pentane (tert. octyl‐isocyanide) with the corresponding transition metal carbonyls Fe₂(CO)₉ and Mn₂(CO)₁₀. In contrast to isostructural compounds with less bulky tert.‐butylisocyanide ligands the cyanide groups in trans‐[Fe(CN)₂(^tOcNC)₄] and trans‐[Mn(CN)(CO)(^tOcNC)₄] do not act as hydrogen bond acceptors towards solvent molecules in the crystal structures. In addition, the corresponding cis‐isomers are configurationally unstable. The reaction of trans‐[Fe(CN)₂(^tOcNC)₄] and trans‐[Ru(CN)₂(^tOcNC)₄] with MnCl₂, NiCl₂ and Co(NO₃)₂ ends up in the formation of cyanide bridged coordination polymers. X‐ray structure determinations of the cobalt compounds reveal different molecular structures. Whereas the former produces highly distorted infinite polymeric chains with the nitrate anions still coordinated to the cobalt centers, the latter forms polymers with the cobalt atoms being coordinated by four ethanol molecules to which the anions are bound via hydrogen bond interactions. The coordination geometries around ruthenium and cobalt in this coordination polymer are therefore nearly perfectly octahedral and tetrahedral, respectively. Measurements of the magnetic susceptibility of the coordination polymers at different temperatures are indicative of weak antiferromagnetic coupling of the paramagnetic centers along the polymeric chains.     

A cyclo‐P6 Ligand Complex for the Formation of Planar 2D Layers

The all‐phosphorus analogue of benzene, stabilized as middle deck in triple‐decker complexes, is a promising building block for the formation of graphene‐like sheet structures. The reaction of [(CpMo)₂(μ,η⁶:η⁶‐P₆)] ( 1 ) with CuX (X=Br, I) leads to self‐assembly into unprecedented 2D networks of [{(CpMo)₂P₆}(CuBr)₄]_n ( 2 ) and [{(CpMo)₂P₆}(CuI)₂]_n ( 3 ). X‐ray structural analyses show a unique deformation of the previously planar cyclo‐P₆ ligand. This includes bending of one P atom in an envelope conformation as well as a bisallylic distortion. Despite this, 2 and 3 form planar layers. Both polymers were furthermore analyzed by ³¹P{¹H} magic angle spinning (MAS) NMR spectroscopy, revealing signals corresponding to six non‐equivalent phosphorus sites. A peak assignment is achieved by 2D correlation spectra as well as by DFT chemical shift computations.     

Reversible Guest Binding in a Non‐Porous FeII Coordination Polymer Host Toggles Spin Crossover

Formation of either a dimetallic compound or a 1 D coordination polymer of adiponitrile adducts of [Fe(bpte)]²⁺ (bpte=[1,2‐bis(pyridin‐2‐ylmethyl)thio]ethane) can be controlled by the choice of counteranion. The iron(II) atoms of the bis(adiponitrile)‐bridged dimeric complex [Fe₂(bpte)₂(μ₂‐(NC(CH₂)₄CN)₂](SbF₆)₄ ( 2 ) are low spin at room temperature, as are those in the polymeric adiponitrile‐linked acetone solvate polymer {[Fe(bpte)(μ₂‐NC(CH₂)₄CN)](BPh₄)₂ ? Me₂CO} ( 3? Me₂CO). On heating 3? Me₂CO to 80 °C, the acetone is abruptly removed with an accompanying purple to dull lavender colour change corresponding to a conversion to a high‐spin compound. Cooling reveals that the desolvate 3 shows hysteretic and abrupt spin crossover (SCO) S=0?S=2 behaviour centred at 205 K. Non‐porous 3 can reversibly absorb one equivalent of acetone per iron centre to regenerate the same crystalline phase of 3? Me₂CO concurrently reinstating a low‐spin state.     

Dipyridylamide Donor Disposition and Isophthalate Substituent Steric Effect on the Dimensionality and Topology of Divalent Copper Coordination Polymers

Divalent copper coordination polymers containing an isophthalate ligand and a dipyridylamide ligand show different dimensionalities and topologies depending on pyridyl nitrogen donor disposition and the steric bulk of the substituent on the dicarboxylate aromatic ring. According to single‐crystal X‐ray diffraction, [Cu(ip)(3‐pna)]_n ( 1 , ip = isophthalate, 3‐pna = 3‐pyridylnicotinamide) shows a (4, 4) layered grid structure based on {Cu₂(OCO)₂} dimeric units. {[Cu(ip)(3‐pina)]·H₂O}_n ( 2 , 3‐pina = 3‐pyridylisonicotinamide) exhibits similar dimeric units, but in contrast to 1 these are connected into a non‐interpenetrated 3D 6⁵8 cds network. Both [Cu(mip)(3‐pina)]_n ( 3 , mip = 5‐methylisophthalate) and [Cu(meoip)(3‐pina)]_n ( 4 , mip = 5‐methoxyisophthalate) display dimer‐based 4¹²6³ pcu networks in contrast to 2 . Use of 5‐hydroxyisophthalate (H₂hip) as a precursor afforded a mixture of {[Cu₂(hip)₂(3‐pina)₄]·9.5H₂O}_n ( 5 ) and [Cu(hip)(3‐pina)]_n ( 6 ). Compound 5 shows a 2D interdigitated structure with [Cu(hip)]_n coordination polymer layers featuring {Cu₂(OCO)₂} dimeric units and pendant 3‐pina ligands, while 6 also showed a dimer‐based 4¹²6³ pcu network. Use of the very sterically bulky 5‐tert‐butylisophthalate (tbip) ligand afforded the 1D chain coordination polymer {[Cu(tbip)(3‐pina)₂(H₂O)]·H₂O}_n ( 7 ), which contains isolated copper ions in contrast to 1 – 6 , and has a curious “butterfly“ resemblance. Very weak antiferromagnetic coupling is seen within the {Cu₂(OCO)₂} dimeric units in 1 . Thermal decomposition behavior is also discussed.     

Heterotrimetallic Coordination Polymers: {CuIILnIIIFeIII} Chains and {NiIILnIIIFeIII} Layers: Synthesis,Crystal Structures,and Magnetic Properties

The use of the [Fe^III(AA)(CN)₄]^? complex anion as metalloligand towards the preformed [Cu^II(valpn)Ln^III]³⁺ or [Ni^II(valpn)Ln^III]³⁺ heterometallic complex cations (AA=2,2′‐bipyridine (bipy) and 1,10‐phenathroline (phen); H₂valpn=1,3‐propanediyl‐bis(2‐iminomethylene‐6‐methoxyphenol)) allowed the preparation of two families of heterotrimetallic complexes: three isostructural 1D coordination polymers of general formula {[Cu^II(valpn)Ln^III(H₂O)₃(μ‐NC)₂Fe^III(phen)(CN)₂ {(μ‐NC)Fe^III(phen)(CN)₃}]NO₃ ? 7 H₂O}_n (Ln=Gd ( 1 ), Tb ( 2 ), and Dy ( 3 )) and the trinuclear complex [Cu^II(valpn)La^III(OH₂)₃(O₂NO)(μ‐NC)Fe^III(phen)(CN)₃] ? NO₃ ? H₂O ? CH₃CN ( 4 ) were obtained with the [Cu^II(valpn)Ln^III]³⁺ assembling unit, whereas three isostructural heterotrimetallic 2D networks, {[Ni^II(valpn)Ln^III(ONO₂)₂(H₂O)(μ‐NC)₃Fe^III(bipy)(CN)] ? 2 H₂O ? 2 CH₃CN}_n (Ln=Gd ( 5 ), Tb ( 6 ), and Dy ( 7 )) resulted with the related [Ni^II(valpn)Ln^III]³⁺ precursor. The crystal structure of compound 4 consists of discrete heterotrimetallic complex cations, [Cu^II(valpn)La^III(OH₂)₃(O₂NO)(μ‐NC)Fe^III(phen)(CN)₃]⁺, nitrate counterions, and non‐coordinate water and acetonitrile molecules. The heteroleptic {Fe^III(bipy)(CN)₄} moiety in 5 – 7 acts as a tris‐monodentate ligand towards three {Ni^II(valpn)Ln^III} binuclear nodes leading to heterotrimetallic 2D networks. The ferromagnetic interaction through the diphenoxo bridge in the Cu^II?Ln^III ( 1 – 3 ) and Ni^II?Ln^III ( 5 – 7 ) units, as well as through the single cyanide bridge between the Fe^III and either Ni^II ( 5 – 7 ) or Cu^II ( 4 ) account for the overall ferromagnetic behavior observed in 1 – 7 . DFT‐type calculations were performed to substantiate the magnetic interactions in 1 , 4 , and 5 . Interestingly, compound 6 exhibits slow relaxation of the magnetization with maxima of the out‐of‐phase ac signals below 4.0 K in the lack of a dc field, the values of the pre‐exponential factor (τ_o) and energy barrier (E_a) through the Arrhenius equation being 2.0×10^?12 s and 29.1 cm^?1, respectively. In the case of 7 , the ferromagnetic interactions through the double phenoxo (Ni^II–Dy^III) and single cyanide (Fe^III–Ni^II) pathways are masked by the depopulation of the Stark levels of the Dy^III ion, this feature most likely accounting for the continuous decrease of χ_M T upon cooling observed for this last compound.     

Density functional investigation and bonding analysis of pentacoordinated iron complexes with mixed cyano and carbonyl ligands

The equilibrium structures and vibrational frequencies of the iron complexes [Fe⁰(CN)_n(CO)_5?n]^n? and [Fe^II(CN)_n(CO)_5?n]^2?n (n = 0–5) have been calculated at the BP86 level of theory. The Fe⁰ complexes adopt trigonal bipyramidal structures with the cyano ligands occupying the axial positions, whereas corresponding Fe²⁺ complexes adopt square pyramidal structures with the cyano ligands in the equatorial positions. The calculated geometries and vibrational frequencies of the mixed iron Fe⁰ carbonyl cyanide complexes are in a very good agreement with the available experimental data. The nature of the Fe? CN and Fe? CO bonds has been analyzed with both charge decomposition and energy partitioning analysis. The results of energy partitioning analysis of the Fe? CO bonds shows that the binding interactions in Fe⁰ complexes have 50–55% electrostatic and 45–50% covalent character, whereas in Fe²⁺ 45–50% electrostatic and 50–55% covalent character. There is a significant contribution of the π‐ orbital interaction to the Fe? CO covalent bonding which increases as the number of the cyano groups increases, and the complexes become more negatively charged. This contribution decreases in going from Fe⁰ to Fe²⁺ complexes. Also, this contribution correlates very well with the C? O stretching frequencies. The Fe? CN bonds have much less π‐character (12–30%) than the Fe? CO bonds. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010     

Synthesis and Characterisation of a New Series of Bistable Iron(II) Spin‐Crossover 2D Metal–Organic Frameworks

Twelve coordination polymers with formula {Fe(3‐Xpy)₂[M^II(CN)₄]} (M^II: Ni, Pd, Pt; X: F, Cl, Br, I; py: pyridine) have been synthesised, and their crystal structures have been determined by single‐crystal or powder X‐ray analysis. All of the fluoro and iodo compounds, as well as the chloro derivative in which M^II is Pt, crystallise in the monoclinic C2/m space group, whereas the rest of the chloro and all of the bromo derivatives crystallise in the orthorhombic Pnc2 space group. In all cases, the iron(II) atom resides in a pseudo‐octahedral [FeN₆] coordination core, with similar bond lengths and angles in the various derivatives. The major difference between the two kinds of structure arises from the stacking of consecutive two‐dimensional {Fe(3‐Xpy)₂[M^II(CN)₄]}_∞ layers, which allows different dispositions of the X atoms. The fluoro and chloro derivatives undergo cooperative spin crossover (SCO) with significant hysteretic behaviour, whereas the rest are paramagnetic. The thermal hysteresis, if X is F, shifts toward room temperature without changing the cooperativity as the pressure increases in the interval 10⁵ Pa–0.5 GPa. At ambient pressure, the SCO phenomenon has been structurally characterised at different significant temperatures, and the corresponding thermodynamic parameters were obtained from DSC calorimetric measurements. Compound {Fe(3‐Clpy)₂[Pd(CN)₄]} represents a new example of a “re‐entrant” two‐step spin transition by showing the Pnma space group in the intermediate phase (IP) and the Pnc2 space group in the low‐spin (LS) and high‐spin (HS) phases.     

Metal Ion‐tuned Complexes based on Benzene‐1, 2, 4, 5‐tetracarboxylic Acid and the Semirigid Ligand 1, 4‐Bis(2‐methylbenzimidazol‐1‐ylmethyl) Benzene

Abstract. Two metal‐organic coordination polymers [Co(bmb)(btc)_0.5]_n( 1 ) and {[Zn(bmb)_0.5(btc)_0.5(H₂O)] · 0.5bmb · H₂O}_n ( 2 ) [H₄btc = benzene‐1, 2, 4, 5‐tetracarboxylic acid, bmb = 1, 4‐bis(2‐methylbenzimidazol‐1‐ylmethyl) benzene] were prepared under hydrothermal conditions. Single‐crystal X‐ray diffraction indicates that both complexes have a 2D framework structure with (4 · 6²) (4² · 6² · 8²) topology. Interestingly, the hydrogen bonds in 2 form a fascinating meso‐helix. The catalytic activity of 1 for oxidative coupling of 2, 6‐dimethylphenol (DMP) and the photoluminescence properties of 2 were investigated. Furthermore, the complexes were investigated by IR spectroscopy and thermogravimetric analysis.     

Hyperbranched polyethyleneimine architecture onto poly(allylamine) by simple synthetic approach and the chelating characters

In resemblance to the ethoxylation of alkylamine or polymeric amines to introduce the nonionic hydrophiles by incorporation of ethylene oxide groups to make surfactants, ethyleneimine (EI) groups were introduced into poly(allylamine) by a simple in situ reaction of this polymer with 2‐chloroethylamine hydrochloride. The resultant polymers were allylic and chain‐pendant with hyperbranched polyethyleneimine. The EI number (n) of the polymers was determined by ¹H NMR. The percentages of primary, secondary, and tertiary amine present were estimated by potentiometric titration. The chelating abilities of the polymers that were applied growth conditions once (G₁, n ≈ 2) and twice (G₂, n ≈ 6) were also examined by potentiometric titration and ultraviolet–visible spectoscopy in the presence of metal ions (Cu⁺²). Continuous‐variation analysis revealed that each repeat unit of G₁ and G₂ behaves as a multident chelate and forms a stable complex with Cu⁺² ions utilizing an average of three EI dents per ion. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3018–3023, 2001