Unilateral exclusion of Jahn-Teller-inactive d5 Mn(H 2O)4(C7H4NO3S) 22+ guests by strongly distorted host d9 Cu(H2O)4(C7H4NO3S) 22+ lattice

Pance Naumov, Ljupčo Pejov, Gligor Jovanovski, Trajče Stafilov, Milena Taseska, Emilija Stojanovska

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The crystal lattice of the isomorphous tetraaquabis(saccharinate)metal(II) dihydrates was employed as a structurally flexible coordination framework capable of sustaining large internal distortions to study the competitive inclusion of Jahn-Teller (JT) distorted d9 ions, [Cu(H 2O)4(sac)2]2+, and JT-inactive d5 ions, [Mn(H2O)4(sac)2] 2+, in binary solid solutions under thermodynamically controlled conditions of statistical mixing (sac = saccharinate anion, C7H 4NO3S-). Probing of the metal content of the solid phase showed a two-regime inclusion profile: increasing the ratio of the distorted cation relative to the undistorted one in the solution phase of up to about 35% results in linear dependence and preferred inclusion of the former with maximum concentration of 100% in the crystal and complete exclusion of the undistorted ion above that point. A mixed crystal with highest copper ratio of 63% was obtained from solution with 25% copper, which under the P21/c crystal symmetry corresponds to sustainable integrity of the undistorted lattice by substitution of up to 2/3 of its sites. This stability limit shows that four out of the six sites around each [Mn(H2O) 4(sac)2]2+ ion can be substituted by distorted [Cu(H2O)4(sac)2]2+ guests under conditions of thermodynamically controlled, statistically averaged exchange. The undistorted host is very tolerant toward inclusion of strongly distorted guests. When acting as host, the distorted ion is more discriminatory toward the undistorted guest. Along with the expectation from the JT theory, structural refinement of seven crystals, including a mixed crystal with composition of [Cu0.126Mn0.874(H2O)4(C 7H4NO3S)2](H2O) 2, showed that metal-hgand distances are significantly affected by the metal substitution. Inclusion of the JT-active ion results in distortion of the coordination polyhedron by increasing the bond length difference between the two metal-O(water) bonds and also causes shortening of the M-N bond. Due to the rigidness caused by π-conjugation, the overall effect on the endocyclic geometry of the organic ligand is small. The anisotropic distortions around the metal ion are faithfully reflected in the stretching force constants of the coordinated water molecules and thus in the IR spectrum of the mixed crystals.

Original languageEnglish (US)
Pages (from-to)1319-1326
Number of pages8
JournalCrystal Growth and Design
Issue number4
StatePublished - Apr 2008

ASJC Scopus subject areas

  • General Chemistry
  • General Materials Science
  • Condensed Matter Physics


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