title: An investigation of photo- and pressure-induced effects in a pair of isostructural two-dimensional spin-crossover framework materials.
abstract: Two new isostructural iron(II) spin-crossover (SCO) framework (SCOF) materials of the type [Fe(dpms)2(NCX)2] (dpms = 4,4'-dipyridylmethyl sulfide; X = S (SCOF-6(S)), X = Se (SCOF-6(Se))) have been synthesized. The 2D framework materials consist of undulating and interpenetrated rhomboid (4,4) nets. SCOF-6(S) displays an incomplete SCO transition with only approximately 30 % conversion of high-spin (HS) to low-spin iron(II) sites over the temperature range 300-4 K (T1/2 = 75 K). In contrast, the NCSe(-) analogue, SCOF-6(Se), displays a complete SCO transition (T1/2 = 135 K). Photomagnetic characterizations reveal quantitative light- induced excited spin-state trapping (LIESST) of metastable HS iron(II) sites at 10 K. The temperature at which the photoinduced stored information is erased is 58 and 50 K for SCOF-6(S) and SCOF-6(Se), respectively. Variable-pressure magnetic measurements were performed on SCOF-6(S), revealing that with increasing pressure both the T1/2 value and the extent of spin conversion are increased; with pressures exceeding 5.2 kbar a complete thermal transition is achieved. This study confirms that kinetic trapping effects are responsible for hindering a complete thermally induced spin transition in SCOF-6(S) at ambient pressure due to an interplay between close T1/2 and T(LIESST) values.
authors.affiliation: School of Chemistry, The University of Sydney, NSW 2006 (Australia), Fax: (+61) 2-9351-5741.
authors.forename: Natasha F
authors.initials: NF
authors.lastname: Sciortino
authors.forename: Suzanne M
authors.initials: SM
authors.lastname: Neville
authors.forename: Cédric
authors.initials: C
authors.lastname: Desplanches
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Létard
authors.forename: Victor
authors.initials: V
authors.lastname: Martinez
authors.forename: José Antonio
authors.initials: JA
authors.lastname: Real
authors.forename: Boujemaa
authors.initials: B
authors.lastname: Moubaraki
authors.forename: Keith S
authors.initials: KS
authors.lastname: Murray
authors.forename: Cameron J
authors.initials: CJ
authors.lastname: Kepert
keywords: chalcogens; coordination polymers; iron; magnetic properties; spin crossover