Single Crystal EPR Study of the Dinuclear Cu(II) Complex [Cu(tda)(phen)]2 ·H2tda (tda ) Thiodiacetate, phen ) Phenanthroline): Influence of Weak Interdimeric Magnetic Interactions

NICOLAS NEUMAN; MIREILLE PEREC; PABLO GONZÁLEZ; MARIO PASSEGGI; ALBERTO RIZZI; CARLOS BRONDINO

JOURNAL OF PHYSICAL CHEMISTRY A

AMER CHEMICAL SOC

Año: 2010 vol. 114 p. 13069 - 13075

1089-5639

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> We report powder and single crystal EPR measurements of [Cu(tda)(phen)]2·H2tda (tda = thiodiacetate, phen = phenanthroline) at 9.7 GHz. This compound consists of centrosymmetric copper(II) ion dimers, weakly ferromagnetically exchange coupled (J = +3.2 cm?1), in which the dimeric units are linked by hydrophobic chemical paths involving the phen molecules. EPR revealed that the triplet spectra are collapsed by interdimeric exchange interactions mediated by that chemical path. Analysis and simulation of the single crystal EPR spectra were performed using Anderson´s exchange narrowing model, together with statistical arguments. This approach allowed us to interpret the spectra modulated by the interdimeric interactions in situations of weak, intermediate, and strong exchange. We evaluated an interdimeric exchange constant J´ = 0.0070(3) cm?1, indicating that hydrophobic paths can transmit weak exchange interactions between centers at relatively long distances of the order of ~ 10 Å.