Patrizia Tomasin

Asymmetric compartmental macrocyclic ligands and related mononuclear and hetero-dinuclear complexes with d- and/or f-metal ions

[1+1] Asymmetric compartmental macrocycles H 2 L (H 2 L A –H 2 L G ), containing one N 2 O 2 , N 3 O 2 or N 2 O 2 O 2 Schiff base and one adjacent O 2 O 3 , O 2 O 4 or O 2 O 5 ‘crown like’ coordination chamber, have been prepared by self-condensation or by reaction of the appropriate diformyl (H 2 L I –H 2 L III ) and amine precursors in the presence of barium(II) salts, followed by a demetallation reaction of the resulting complexes, Ba(H 2 L)(ClO 4 ) 2 , with guanidinium sulphate. They have been characterised by IR, NMR and mass spectrometry. The single crystal X-ray structural determination of H 2 L C confirms their [1+1] cyclic nature. The mononuclear complexes Ln(H 2 L)(X) 3 · n S (Ln=La-Lu; X=Cl − , NO 3 − ) and Ni(L)· n S have been prepared by reaction of the preformed ligands with the appropriate metal salt, by template procedure or by condensation of the acyclic complexes with the diformyl derivatives Ln(H 2 L′)(X) 3 or Ni(L′) with the appropriate amine. They have been characterised by IR, NMR, magnetic susceptibility and mass spectrometry. In these mononuclear complexes the 4f and transition metal ion invariantly occupy respectively, the crown-like and the Schiff base chamber. In [La(H 2 L C )(H 2 O) 4 ]Cl 3 the single crystal X-ray structure reveals that a bicapped square antiprismatic decacoordination about the central metal ion is reached by the coordination of the oxygen atoms of the crown-ether chamber and by the oxygen atoms of four water molecules. A Schiff base occupancy has been obtained by the lanthanum ion only when Ba(H 2 L)(ClO 4 ) 2 was used instead of the free ligand H 2 L: the barium ion remains in the crown-ether chamber and obliges the incoming lanthanum ion to fill the Schiff base site. By this procedure the hetero-dinuclear complex, LaBa(L D )(ClO 4 ) 2 (OH)·3H 2 O, has been obtained. La(H 2 L C )(Cl) 3 , by reaction with the appropriate metal salt, gives rise to the hetero-dinuclear species MLa(L C )(Cl) 2 (OH)· n H 2 O (M=Cu, n =1; M=Ni, n =2). LaNa(L D )(X) 2 ·(X=Cl, NO 3 ) and LaNa(L F )(NO 3 ) 2 have been synthesised by template procedure or by reaction of H 2 L D or H 2 L F with the appropriate lanthanum(III) salt and sodium hydroxide.

Functionalized acyclic Schiff bases and related complexes with d- and f-metal ions

Abstract The condensation reaction in acetonitrile of 2,6-diformyl-4-chlorophenol with tris-(2-aminoethyl)amine forms the [3+1] macroacyclic Schiff base H 3 -I which reacts with LnCl 3 ·n n H 2 O (Ln = La 3+ , Dy 3+ , Gd 3+ ) in the presence of Net 3 giving rise to Ln( I )· n S (S = H 2 O, dmf, CH 3 CN: n =0–1.5). Crystals of La( I ) (dmf), grown from a dimethylformamide/acetonitrile solution, are monoclinic, space grop P 2 1 /c with a = 12.590(4) , b = 14.277(5), c = 19.710(5)A, β=95.45° and Z = 2. This complex is a dimeric entity and shown an inversion center in between the two lanthanum(III) ions. The organic ligand coordinates to one lanthanum ion through the four nitrogen and the three phenoxide oxygen atoms while it links the second lanhanum ion through one aldehydic oxygen atom: the other two aldehydic oxygens are not involved in the coordination and do not form significative interactions with neighboring molecules. Thus each dinuclear complex behaves as an isolated entity. The nonacoordination around each metal ion is reached through the additional coordination of the oxygen atom of a dimethylformamide molecule. The three LaN (iminic) bond distances fall between 2.70 and 2.79 A, while the LaN (aminic) bond is longer (2.86 A). Similarly the LaO (phenolic) bonds distances are in the range 2.41–2.47 A, considerably shorter than the LaO (aldehydic) which is 2.72 A, while the LaO (dimethylformamide) is 2.55 A. Finally the two lanthanum atoms are 8.24 A apart. 2,6-Diformyl-4-chlorophenol reacts in CH 4 CN with H 2 NRNH 3 to give the [2 + 1] acyclic Schiff bases H 2 -II . The corresponding complexes containing a d (nickel(II) Ni( II ), or manganese(III) Mn( II )(OH), and (lanthanum(III), gadohnium(III), dysprosium(III)) Ln( H 2 -II )(NO 3 ) 4 or the uranyl(VI) ion, UO 2 ( II )(MeOH), UO 2 ( H-II )(NO 4 ) and UO 2 ( H 2 -II )(NO 4 ) 2 have also been prepared by reaction of these ligands with the appropriate metal salts or by template procedure, the different content of the nitrate in the uranyl(VI) complexes depending on the amount of base used. These complexes may be converted into the acetal analogues in alcoholic solution. Similarly the condensation of 3-methoxy-2-hydroxybenzaldehyde or 3-ethoxy-2-hydroxybenzaldehyde with tris-(2-aminoethyl)amine in a 1:3 molar ratio afforded Schiff bases H 3 -IV and H 3 -V which react with lanthanide(III) salt to give rise, respectively, in the presence or in the absence of the appropriate amount of base, to Ln( IV )· n H 2 O and Ln( V )· n H[in2O and Ln( H 3 -IV )(X) 4 ·n n H 2 O or Ln( H 3 -V ) (X) 3 · n H 2 O (Ln=La 3+ , Gd 3+ ; X=Cl, NO 4 6 ; n = 1–5. These complexes are no longer stable in solution and hydrolyzed especially when redissolved in alcohol. H 3 -I , H 2 -II and/or the related complexes have been engaged in further condensation reactions with 2-aminomethyl-12-crown-4 or 2-aminomethyl-15-crown-5 to give rise to the functionalized Schiff bases ( H 3 -III and H 2 -VII ) and related d- or f-complexes. Moreover the functionalized ligands H 3 -VI, H 2 -VIII, H 2 -X and H 2 -XI and/or the related d- or f-complexes have been synthesized by condensation of the appropriate formyl and amine precursors. The ligands and the complexes have been characterized by physico-chemical measurements, especially by IR and NMR spectroscopy, SEM and EDX investigation, and FAB mass spectrometry.

Novel Schiff base compounds containing calix[4]arene

Abstract New cyclic and acyclic Schiff bases have been prepared by condensation reaction of 5,17-diamino-25,26,27,28-tetrapropoxycalix[4]arene (L B ) with 2,6-diformyl-4-chlorophenol and 1,5-diamino-3-aza(methyl)pentane or with 2,3-dihydroxybenzaldehyde. The related complexes containing d- or f-metal ions have been obtained by reaction of the preformed ligands with the appropriate metal salt or by a template macrocyclic synthesis. The hetero-polynuclear complexes have been synthesized by a step by step procedure. Condensation of 5,17-diformyl-25,27-dipropoxycalix[4]arene (L A ) with tris(2-aminoethyl)amine affords a macrobicyclic ligand containing three calixarene units. The ligands and the related complexes have been characterized by elemental analyses, IR or NMR spectroscopy and mass spectrometry. The stoicheiometries of the complexes have been assigned by SEM and EDX investigations.

Heterodinuclear LnNa Complexes with an Asymmetric Macrocyclic Compartmental Schiff Base

Heterodinuclear lanthanide(III)-sodium(I) complexes [LnNa(L)-(Cl) 2 (CH 3 OH)] (Ln = La - Nd, Sm - Lu), where H 2 L is a [1+1] asymmetric compartmental macrocyclic ligand containing a N 3 O 2 Schiff base and a O 3 O 2 crown-ether-like coordination site, have been prepared and characterized by IR, 1 H, 1 3 C, and 2 3 Na NMR spectroscopy, mass spectrometry, and electron microscopy. In the solid state, the lanthanide(III) ions coordinate the Schiff-base N 3 O 2 site, and the sodium ion occupies the O 3 O 2 crownlike cavity, as shown by the X-ray crystal structures of the Nd, Eu, Gd, and Yb derivatives. In these complexes, the lanthanide(III) ion is coordinated by two chlorine atoms in the trans position and by three nitrogen and two negatively charged phenol oxygen atoms of the Schiff base, and the ion is heptacoordinated with a pentagonal bipyramidal geometry. The sodium ion is coordinated by three etheric oxygen atoms and the two phenolic oxygens that act as a bridge. A methanol molecule is also coordinated in the apical position of the resulting pentagonal pyramidal polyhedron. A detailed 1 H and 1 3 C NMR study was carried out in CD 3 OD for both diamagnetic and paramagnetic heterodinuclear complexes [LnNa(L)(Cl) 2 (CH 3 OH)]. The complexes are also isostructural in solution, and their structures parallel those found in the solid state. Moreover, some significative distances determined in the solid state and in solution are comparable. Finally, the potential use of these complexes as molecular probes for the selective recognition of specific metal ions has been tested. In particular, their ability to act as shift reagents and the selectivity of the O 3 O 2 site towards Li t , Ca 2 + , and K + were investigated by 2 3 Na NMR spectroscopy.

Lanthanide (III) complexes with a podand Schiff base containing an N4O3 coordination site

Abstract New lanthanide complexes [Ln(L) (dmf)] 2 with a podand Schiff base ligand H 3 L have been prepared by [3 + 1] condensation of 2,6-diformyl-4-chlorophenol and tris-(2-aminoethyl)amine in the presence of Ln(Cl) 3 · n H 2 0 (Ln = La, Gd and Dy) and NEt 3 . The lanthanide(III) ions coordinate into the inner N 4 O 3 chamber of the ligand bearing three free carbonyl groups which may be involved in further functionalization.

Lanthanide(III) macroacyclic and macrocyclic Schiff base complexes containing oxamidic groups

Abstract The macroacylic Schiff bases containing oxamidic groups have been prepared by [2+1] condensation of N , N ′-bis-(2-aminoethyl)oxamido (H 2 L A , respectively, with 2-hydroxybenzaldehyde (H 4 L B ) or 2,6-diformyl-4-chlorophenol (H 4 L C ) and their properties studied by IR, NMR and mass spectrometry. The complexation behaviour of the formyl and amino-amide precursors H 2 L A and of the Schiff bases H 4 L B and H 4 L C towards lanthanide(III) salts was studied and the resulting mononuclear or polynuclear complexes characterised by IR and NMR spectroscopy. H 4 L B forms, when reacted with copper(II) salts in a methanol/dimethylformamide solution, the more soluble green mononuclear Cu(H 2 L B ) and the less soluble violet homodinuclear Cu 2 (L B ) complexes, which have been separated by subsequent crystallization. Magnetic susceptibility measurements evidence a strong antiferromagnetic interaction between the two copper ions in the dinuclear complex. The macrocyclic Schiff bases H 6 L D H 6 L G were also synthesised by [2+2] condensation of N , N ′-bis(2-aminoethyl)oxiamido or N , N ′-bis(2-amino-1,1-dimethylethyl)oxamido with 2,6-diformyl-4-chlorophenol or 2,6-diformyl-4-methylphenol. H 6 L D H 6 L G have been characterised by elemental analyses, IR, NMR; their cyclic nature was inferred especially by FAB mass spectrometry. They form homodinuclear or polynuclear lanthanide(III) and yttrium(III) complexes when reacted with Ln(NO 3 ) 3 · n H 2 O (Ln = Dy 3+ , Gd 3+ , La 3+ , Y 3+ ). The homodinuclear complexes Ln 2 (HL)(NO 3 ) can give rise to heteropolynuclear copper(II)-lanthanide(III) complexes when reacted with copper(II) salts.

New Complexes of Ditopic Ligands with “d” and/or “s” Metal Ions

Abstract The asymmetric compartmental macrocycles containing one N2O2 or N3O2 Schiff base and one O2O3 or O2O4 crown-ether like chamber, have been obtained by condensation reaction of the formyl precursors 3,3′-(3-oxapentane-1, 5-diyldioxy) bis (2-hydroxybenzaldehyde) or 3,3′-(3,6-dioxaoctane-1,8-diyldioxy)-bis(2-hydroxybenzaldehyde) with ethyl ethylenediamine (H2LA, H2LC), 1,5-diamino-3-azamethylpentane(H2LB, H2LD), also in the presence of metal ions as templating agents. These ditopic ligands, with dissimilar coordination sites, have been designed and used for the selective complexation of “d” and/or “s” metal ions, respectively into the Schiff base and the crown ether chamber. The selectivity of these processes strongly depends on the size and on the donor atom sets of the sites. The possibility to obtain mononuclear M(L)·nH2O (M = Ni2+, Cu2+, Co2+), Mn(L)(CH3COO)·nH2O or Na(L) and hetero-dinuclear MNa(L)(CH3COO) (M = Ni2+, Cu2+, Co2+) and MnNa(L)(CH3COO)2·nH2O complexes has been successfully tested. The ligands and complexes have been characterized by ir, nmr, mass spectrometry and magnetic susceptibility measurements. Two of the ligands used for the preparation of the solid samples, i.e., to H2LA and H2LB, have been employed to study complexation reactions of Co(II) and Na(I) in solution. In order to obtain information on the ligand preorganization effect toward the complex stabilities, a simpler open chain parent compound of H2LB (H2LE) has been also prepared and studied. FT-IR spectra show that H2LA is unable to complex Na+ in DMSO while the complexation reactions of Na+ by H2LB and of Co2+ by H2LA take place with slow kinetics. Therefore, thermodynamic data have been obtained only for the systems Co2+/H2LB and Co2+/H2LE. The thermodynamic parameters obtained for the complexation reactions show that the pre-organization of the donor atoms in H2LB does not add a significant contribution to the stabilities of the complexes. Both H2LB and H2LE form in DMSO 1:1, 1:2 and 1:3 = M:L complexes with very similar stabilities and almost equal enthalpies of formation. Physico-chemical studies suggest besides that the slow reaction of Na+ with H2LB is probably due to the formation of a 1:1 complex where the metal cation, initially occupying the O3 cage of the ligand, slowly binds also the oxygens of the phenolic moieties. Spectral and calorimetric data on solutions containing H2LB and different Co2+: Na+ ratios evidence that in DMSO no stable heterodinuclear complexes form when the neutral ligand is considered.

Complexation behaviour and stability of Schiff bases in aqueous solution. The case of an acyclic diimino(amino) diphenol and its reduced triamine derivative

The copper(II), nickel(II), and zinc(II) complexes of the acyclic Schiff base H(2)L(A), obtained by [1 + 2] condensation of 1,2-ethanediamine,N-(2-aminoethyl)-N-methyl with 3-ethoxy-2-hydroxybenzaldehyde, and of H(2)L(B), the reduced derivative of H(2)L(A), were prepared and their properties studied by IR, NMR and SEM-EDS. In these complexes, the metal ion is always located in the coordination chamber of the ligand delimited by two phenol oxygens and nitrogen atoms (either aminic or iminic). The coordination behaviour of H(2)L(A) and H(2)L(B) towards H(+), Cu(2+), Ni(2+) and Zn(2+) in aqueous solution at 298 K and mu = 0.1 mol dm(-3) (Na)ClO(4) was also studied by potentiometric, NMR and UV-VIS measurements. In particular, potentiometric equilibrium studies indicate that H(2)L(A) is not stable enough to have a pH range in which it is the sole species in aqueous solution. In such a solution, the Schiff base forms over a limited pH range, between 6 and 10, with a maximum formation percentage at pH approximately 9. In addition, the involvement of imine nitrogens in the complexes markedly stabilises the azomethylene linkage, so that the metal complexes of H(2)L(A), particularly those of copper(II), are the species largely prevailing in solutions with pH >3.5. The stability constants of the complexes formed by metal ions with H(2)L(A) and H(2)L(B) follow the order Cu(2+) >> Ni(2+) > Zn(2+); distribution plots show that copper(II) gives complexes more stable with H(2)L(A), whereas Ni(2+) and Zn(2+) prefer the reduced ligand, H(2)L(B).

Hetero-dinuclear sodium–lanthanide(III) complexes with an asymmetric compartmental macrocycle

A heterodinuclear macrocyclic complex containing both Yb3+ and Na+ ions has been synthesized and characterized by X-ray crystallography and 1H and 23Na solution NMR; at room temperature the coordinated Na+ ion is in slow chemical exchange with free Na+ ions and its NMR resonance is strongly shifted.