Crystal Engineering and Photomagnetic Studies of CN-Bridged Coordination Polymers Based on Octacyanidometallates(IV) and [Ni(cyclam)]²⁺

Abstract

A series of new CN-bridged coordination networks of different dimensionality and topology was obtained through the modification of reaction conditions between [Ni(cyclam)] 2+ (cyclam = 1,4,8,11-tetraazacyclotetradecane) and [W(CN) 8 ] 4– . The factors determining the reaction pathway are temperature and addition of the LiCl electrolyte. The products include three negatively charged frameworks incorporating Li + guests: the 1D Li 2 [Ni(cyclam)][W(CN) 8 ]·6H 2 O ( 1 ) straight chain, the 1D Li 2 [Ni(cyclam)][W(CN) 8 ]·2H 2 O ( 2 ) zigzag chain, and the 2D Li 2 [Ni(cyclam)] 3 [W(CN) 8 ] 2 ·24H 2 O ( 3 ) honeycomb-like network, as well as the 3D two-fold interpenetrating [Ni(cyclam)] 5 [Ni(CN) 4 ][W(CN) 8 ] 2 ·11H 2 O ( 4 ) network and the 1D [Ni(cyclam)][Ni(CN) 4 ]·2H 2 O ( 5 ) chain, which result from partial decomposition of the starting complexes. Together with the previously characterized 3D [Ni(cyclam)] 2 [W(CN) 8 ]·16H 2 O ( 6 ) network, they constitute the largest family of CN-bridged coordination polymers obtained from the same pair of building blocks. All compounds exhibit paramagnetic behavior because of the separation of paramagnetic nickel(II) centers through the diamagnetic polycyanidometallates. However, the presence of the photomagnetically active octacyanidotungstate(IV) ions allowed observation of the magnetic superexchange after the violet light excitation (405 nm) for compound 3 , which constitutes the first example of the photomagnetic effect in a Ni II –[W IV (CN) 8 ] system. The photomagnetic investigations for fully hydrated and dehydrated sample of 3 , as well as for the isostructural octacyanidomolybdate(IV)-based network are discussed.

Switching of magnetic properties by topotactic reaction in a 1D CN-bridged Ni(ii)–Nb(iv) system

“…We have previously proved that it is possible to obtain as many as six various coordination systems based on [Ni(cyclam)] 2+ and [W(CN) 8 ] 4− by the manipulation of the above factors. 23 The reaction between [Ni(cyclam)] 2+ and [Nb(CN) 8 ] 4− performed in water solution leads to the formation of a neutral coordination network of the formula [Ni(cyclam)] 2 [Nb(CN) 8 ]· n H 2 O, 32 which is the most thermodynamically stable phase. When the reaction is carried out in the presence of additional electrolytes at room temperature, the incorporation of appropriate cations into the coordination framework was observed.…”

“…In contrast to the straight chain compound 1 , the zigzag-shaped compound 2 could not be obtained in pure form from solution reaction. The synthesis of an isotypic zigzag-shaped chain based on [W(CN) 8 ] 4− ions 23 was performed at 105 °C. This synthetic procedure could not be adopted, since such high temperature causes decomposition of the more fragile [Nb(CN) 8 ] 4− ion.…”

“…For the W IV -based precursor we have obtained as many as five coordination polymers of different topology and dimensionality, which include a 3D diamond-like network [Ni(cyclam)] 2 [W(CN) 8 ]·16H 2 O, a microporous 2D honeycomb-like network incorporating Li + ions Li 2 [Ni(cyclam)] 3 [W(CN) 8 ] 2 ·24H 2 O, a 3D two-fold interpenetrating network [Ni(cyclam)] 5 [Ni(CN) 4 ][W(CN) 8 ] 2 ·11H 2 O formed as a result of rearrangement of the building blocks, as well as 1D linear and zigzag-shaped chains. 23 Mo IV -based analogues comprise 3D and 2D structures 24 and show interesting photomagnetic properties modified by water sorption. 23 By replacing the diamagnetic octacyanidometallates of Mo IV and W IV with paramagnetic [Nb(CN) 8 ] 4− ions we have constructed a series of 2D honeycomb-like frameworks with tuneable magnetic properties by incorporation of different guest cations.…”

“…23 Mo IV -based analogues comprise 3D and 2D structures 24 and show interesting photomagnetic pro-perties modified by water sorption. 23 By replacing the diamagnetic octacyanidometallates of Mo IV and W IV with paramagnetic [Nb(CN) 8 ] 4− ions we have constructed a series of 2D honeycomb-like frameworks with tuneable magnetic properties by incorporation of different guest cations. 25,26 Here we present the first alternating bimetallic chain composed of octacyanidoniobate(IV) and Ni(II) ions, obtained by the synthetic strategy based on the addition of non-coordinating s-block cations at elevated temperature.…”

“…25,26 Here we present the first alternating bimetallic chain composed of octacyanidoniobate(IV) and Ni(II) ions, obtained by the synthetic strategy based on the addition of non-coordinating s-block cations at elevated temperature. 23…”