Extended Huckel (EH) calculations on Mg, Zn, Cu, Ni, Fe, Mn, and VO complexes of phthalocyanine and tetrazaporphin are reported and the results compared to similar calculations on porphyrins The smaller ring size of phthalocyanine gives rise to a larger ligand field The bridge nitrogen atoms give rise to n - π
* transitions, which are probably in the region of the Soret band In Ni, Co, Fe, and Mn there is strong mixing of the bridge N2p

 σ
 and metal b

 2g
 (d

 xy
 ), which should affect the ligand field Extra absorption bands observed in the near uv of NiPc and CoPc are attributed to d

 π
 → π
* transitions A general symmetrized EH program is reported that speeds calculations on large systems

Porphyrins XXVIII. Extended Hückel calculations on metal phthalocyanines and tetrazaporphins

Magnetic anisotropy, magnetization, and average magnetic susceptibility have been measured for iron (II) phthalocyanine. The anisotropy was measured from the room temperature to about 90°K, the average susceptibility from 296 to 1.57°K, and the magnetization was measured at 1.57°K for field strengths between 1100 and 15 000 Oe. The results are interpreted in terms of a 3B2g ground state with a zero‐field splitting parameter D = 64 cm−1, and g‖ = g⊥ = 2.74. Iron (II) phthalocyanine is an unusual example in which a large magnetic anisotropy arises entirely from the zero‐field splitting. The danger inherent in the existing method of evaluation of ligand‐field parameters from the average magnetic susceptibility data has been highlighted, and the advantages of magnetic anisotropy studies in deducing the ligand‐field parameters and the electronic structures are discussed. A change of about 70° of the “setting angle” between 290 and 90°K is observed in this crystal when measured with b axis vertical. It is shown...

Paramagnetic Anisotropy, Low Temperature Magnetization, and Electronic Structure of Iron(II) Phthalocyanine

New discotic metallomesogens of 2,3,7,8,12,13,17,18-octakis (alkyl-thio) 5,10,15,20 tetraaza porphyrin (H2Pn) and some related complexes, obtained by reaction of first row transition metal ions Ni(II), Co(II), Cu(II), Zn(II) with the free porphyrin, have been prepared. All materials were characterized by DSC measurements and optical observations. The microscopic structure of all mesophases was checked and characterized by X-ray diffraction. Except for H2P(7–12), all of the compounds are mesogenic; a few of them exhibit mesomorphic polymorphism. Melting (C→D) temperatures range from 40 to 85°C. Only NiP4, CoP4 and CuP4 show higher values. Both temperature and ΔH of isotropization (D→I) show a regular trend with respect to the number of carbon atoms in the alkyl chains and of the nature of the metal. ΔH values for complexes with partially filled d-shell metals are very similar and show definite differences with respect to those of Zn(II). Optical and X-ray data in the case of n  7 indicate a colum...

Discotic mesomorphism of 2,3,7,8,12,13,17,18-octakis (alkyl-thio) 5,10,15,20 tetraaza porphyrin and its complexes with some divalent transition metal ions Synthesis and characterization

Stereochemistry and properties of the M(II)N(py) coordination bond in the low-spin dipyridinated iron(II) and cobalt(II) phthalocyanines

The first paramagnetic 4d transition-metal complex with a redox-active tetrathiafulvalene ligand has been synthesized. The preparation, X-ray structure, electrochemistry, and electron paramagnetic resonance measurements of [Ru(salen)(PPh 3 )(TTF-CH=CH-Py)](BF 4 ) [1(BF 4 )] are reported. The crystal structure reveals that the paramagnetic Ru ||| (s = ½) center is in a tetragonally elongated octahedral geometry and the TTF-CH=CH-Py ligand is coordinated to the axial position of the Ru ||| ion through the nitrogen atom of the pyridine group. Thus, 1(BF 4 ) is an attractive precursor to study future π-4d interactions in dual-property conducting and magnetic materials.

First Paramagnetic 4d Transition-Metal Complex with a Redox-Active Tetrathiafulvalene Derivative, [Ru(salen)(PPh3)(TTF-CH=CH-Py)]BF4 [salen2-= N,N-Ethan-1,2-diylbis(salicylidenamine), PPh3= Triphenylphosphine, TTF-CH=CH-Py = 4-(2-Tetrathiafulvalenylethenyl)pyridine]

S. Mitra

Papers

Paramagnetic anisotropy and ground state of β-cobalt(II) phthalocyanine

The paramagnetic anisotropy and axial ligand field in complexes with the 2T2g cubic field ground term