Spin-crossover in [Fe(Quinazoline)2][Fe(CN)5NO]. Evidence of its framework flexibility

Spin crossover in Hofmann-like coordination polymers. Effect of the axial ligand substituent and its position

“…[80][81][82][83] This relaxation method has been previously validated by us from the refined crystal structures for both HS and LS phases. 39,54,55,57,58 Additional details on the computational methodology and software package used are available from MS2, ESI. †…”

“…In these solids, the CN ligands at their N ends can be combined with appropriate organic ligands for tuning the energy splitting between the t 2g and e g orbitals to make possible the HS -LS transition. Of that family of solids, the SCO has been reported for ferrous tetracyanides; [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] copper(I), 42 silver(I), 43 and gold(I) dicyanides; 44 octacyanides; [45][46][47] nitroprussides, [48][49][50][51][52][53][54][55][56][57][58] and other cyanide-based 3d transition metal coordination polymers. 59,60 We believe that enough qualitative information is available on the SCO in these coordination polymers to rationalize ligand and metal effects in order to design materials with the desired behavior.…”

Thermally-induced spin-crossover (SCO) in Fe(4-ethynylpyrdine)2[Fe(CN)5NO]. Why is the SCO observed in 2D ferrous nitroprussides despite the NO–NC repulsive interaction in the interlayer region?

“…The thermal decomposition of pillared ferrous nitroprussides remains documented from previous studies. 2,[16][17][18][19][20][21][22][23] The IR spectra and TG curves suggest a Fe(4EPy) 2 [Fe(CN) 5 NO]Á1.5H 2 O formula unit for the material under study. This formula unit is supported by the results of the elemental chemical analysis (Table S2, ESI †).…”

“…2 The large number of studies reported for the spin crossover (SCO) in Hofmann-type Fe(L) 2 [M(CN) 4 ] solids with M = Ni, Pd, Pt, and with L being pyridine and some of its derivatives, [3][4][5][6][7][8][9][10][11][12][13][14][15] stimulated the evaluation of pillared 2D ferrous nitroprussides as potential SCO materials with surprising results. [16][17][18][19][20][21][22][23] Unlike [M(CN) 4 ] building block, in the formed 2D solids with the complex nitroprusside ion, the NO group and the axial CN remain as dangling ligands occupying the interlayer region. Their O and N ends are charge centers related to the p-back bonding interaction of these two ligands with the iron atom.…”

“…2 Although these are adverse factors for the HS -LS spin transition, the SCO has been observed for many pillared 2D ferrous nitroprussides. [16][17][18][19][20][21][22][23]25 The reason for such unexpected behavior is discussed in this contribution.…”