Impact of the synthetic approach on the magnetic properties and homogeneity of mixed crystals of tunable layered ferromagnetic coordination polymers.

Reaction of Co(NCS)2 and Ni(NCS)2 with 4-tert-butylpyridine in ethyl acetate leads to the formation of mixed crystals of a layered compound with the composition [CoxNi1-x(NCS)2(4-tert-butylpyridine]n. The mixed crystal formation was investigated by a combination of atomic absorption spectroscopy, X-ray powder diffraction and IR spectroscopy. Magnetic and specific heat measurements prove dominating ferromagnetic exchange interactions within the layers and a ferromagnetic transition. Depending on the synthetic method, inhomogeneous samples were obtained, for which predominantly the large difference in the solubility of the homometallic compounds might be responsible. Very long reaction time leads to much better samples for which a distinct critical temperature is observed that increases smoothly with increasing Ni content.

Crystal structure, synthesis and thermal properties of bis-(4-benzoyl-pyridine-κN)bis-(iso-thio-cyanato-κN)bis-(methanol-κN)iron(II).

In the crystal structure of the title compound, [Fe(NCS)2(C12H9NO)2(CH4O)2], the FeII cations are octa-hedrally coordinated by two N atoms of 4-benzoyl-pyridine ligands, two N atoms of two terminal iso-thio-cyanate anions and two methanol mol-ecules into discrete complexes that are located on centres of inversion. These complexes are linked via inter-molecular O-H⋯O hydrogen bonds between the methanol O-H H atoms and the carbonyl O atoms of the 4-benzoyl-pyridine ligands, forming layers parallel to (101). Powder X-ray diffraction proved that a pure sample was obtained but that this compound is unstable and transforms into an unknown crystalline phase within several weeks. However, the solvent mol-ecules can be removed by heating in a thermobalance, which for the aged sample as well as the title compound leads to the formation of a compound with the composition Fe(NCS)2(4-benzoyl-pyridine)2, which exhibits a powder pattern that is similar to that of Mn(NCS)2(4-benzoyl-pyridine)2.

Crystal structure, synthesis and thermal properties of bis-(aceto-nitrile-κN)bis-(4-benzoyl-pyridine-κN)bis-(iso-thio-cyanato-κN)nickel(II).

In the crystal structure of the title com-pound, [Ni(NCS)2(CH3CN)2(C12H9NO)2] or Ni(NCS)2(4-benzoyl-pyridine)2(aceto-nitrile)2, the NiII ions are octa-hedrally coordinated by the N atoms of two thio-cyanate anions, two 4-benzoyl-pyridine ligands and two aceto-nitrile mol-ecules into discrete com-plexes that are located on centres of inversion. In the crystal, the discrete com-plexes are linked by centrosymmetric pairs of weak C-H⋯S hydrogen bonds into chains. Thermogravimetric measurements prove that, upon heating, the title com-plex loses the two aceto-nitrile ligands and transforms into a new crystalline modification of the chain com-pound [Ni(NCS)2(4-benzoyl-pyridine)2], which is different from that of the corresponding CoII, NiII and CdII coordination polymers reported in the literature. IR spectroscopic investigations indicate the presence of bridging thio-cyanate anions but the powder pattern cannot be indexed and, therefore, this structure is unknown.

Crystal structure, synthesis and thermal properties of tetra-kis-(4-benzoyl-pyridine-κN)bis-(iso-thio-cyanato-κN)iron(II).

The asymmetric unit of the title compound, [Fe(NCS)2(C12H9NO)4], consists of an FeII ion that is located on a centre of inversion, as well as two 4-benzoyl-pyridine ligands and one thio-cyanate anion in general positions. The FeII ions are coordinated by two N-terminal-bonded thio-cyanate anions and four 4-benzoyl-pyridine ligands into discrete complexes with a slightly distorted octa-hedral geometry. These complexes are further linked by weak C-H⋯O hydrogen bonds into chains running along the c-axis direction. Upon heating, this complex loses half of the 4-benzoyl-pyridine ligands and transforms into a compound with the composition Fe(NCS)2(4-benzoyl-pyridine)2, that might be isotypic to the corresponding MnII compound and for which the structure is unknown.

Crystal structure of bis(4-benzoyl-pyridine-κN)bis(methanol-κO)bis(thio-cyanato-κN)nickel(II) methanol monosolvate.

The asymmetric unit of the title compound, [Ni(NCS)2(C12H9NO)2(CH3OH)2]·CH3OH, comprises one NiII cation, two thio-cyanate anions, two 4-benzoyl-pyridine coligands, two coordinating, as well as one non-coordinating methanol mol-ecule. The NiII cation is coordinated by two terminally N-bonded thio-cyanate anions, the N atoms of two 4-benzoyl-pyridine coligands and the O atoms of two methanol ligands within a slightly distorted octa-hedron. Individual complexes are linked by inter-molecular O-H⋯S hydrogen bonding into chains parallel to [010] that are further connected into layers parallel to (10) by C-H⋯S hydrogen bonds. Additional C-H⋯O hydrogen-bonding inter-actions lead to the formation of a three-dimensional network that limits channels extending parallel to [010] in which the non-coordinating methanol mol-ecules are located. They are hydrogen-bonded to the coordinating methanol mol-ecules. X-ray powder diffraction revealed that the compound could not be prepared as a pure phase.

Tetra-kis(4-benzoyl-pyridine-κN)bis-(iso-thio-cyanato-κN)manganese(II).

The asymmetric unit of the title compound, [Mn(NCS)2(C12H9NO)4], consists of one MnII cation located on a centre of inversion, one thio-cyanate anion and two 4-benzoyl-pyridine co-ligands. The MnII cation is octa-hedrally coordinated by two terminally N-bonded anionic ligands and four N-bonded 4-benzoyl-pyridine co-ligands within a slightly distorted octa-hedron. Individual complexes are linked by inter-molecular C-H⋯O hydrogen-bonding inter-actions into chains running along the c-axis direction. Simultaneous thermogravimetry and differential scanning calorimetry measurements reveal a decomposition in two separate steps, in each of which two co-ligands are removed. The compound obtained after the first step has the composition [Mn(NCS)2(C12H9NO)2] and is of unknown structure, before in the second step decomposition into [Mn(NCS)2] is observed. Magnetic susceptibility measurements show the MnII cations to be in the high-spin state, and that weak anti-ferromagnetic inter-actions between the complexes are present.

Diagnosis and monitoring of colorectal cancer by L6 blood serum polymerase chain reaction is superior to carcinoembryonic antigen-enzyme-linked immunosorbent assay.

PURPOSE: The aim of this study was to compare carcinoembryonic antigen levels with detection of messenger ribonucleic acid coding for the tumor-associated antigen L6 in patients with colorectal cancer. Not only are carcinoembryonic antigens expressed by the corresponding tumor cell, but the messenger ribonucleic acid of tumor-associated antigens, in contrast, is produced exclusively by viable tumor cells. METHODS: L6 messenger ribonucleic acid was determined by reverse-transcription polymerase chain reaction. Carcinoembryonic antigen was measured by the enzyme-linked immunosorbent assay technique, with a cutoff value of 40 microg/l. Blood serum was sampled from 187 patients with colorectal cancer. Statistical significance was calculated with the McNemar chi-squared test. RESULTS: Preoperatively, 79 percent of patients in all stages were positive for L6 messenger ribonucleic acid, whereas only 35 percent had elevated carcinoembryonic antigen titers (P < 0.001). In Dukes A tumors, 84.9 percent of patients were positive for L6 messenger ribonucleic acid, whereas carcinoembryonic antigen was elevated in only 16.9 percent of patients. Only in Dukes D tumors did the enzyme-linked immunosorbent assay for carcinoembryonic antigen exhibit the same sensitivity as reverse-transcription polymerase chain reaction for L6 messenger ribonucleic acid. Recurrence was detected significantly earlier by reverse-transcription polymerase chain reaction for L6 messenger ribonucleic acid than by enzyme-linked immunosorbent assay for carcinoembryonic antigen. CONCLUSION: L6 is more sensitive and precise than carcinoembryonic antigen in diagnosing and monitoring colorectal cancer.