Research (研究方向)

As an important class of inorganic-organic hybrid materials, metal phosphonates have received increasing attentions in the past two decades owing to their potential applications in ion-exchange and absorption, catalysis, proton conductivity and optics etc. We focus on the assembly of new metal phosphonate materials with novel architectures and interesting physical and chemical properties. Particular attentions are being paid on the paramagnetic 3d and 4f systems in order to discover excellent molecule-based magnets, chiral or polar materials in order to explore new optical and multifunctional materials, and proton conductors for fuel cell applications.

作为一类重要的无机-有机杂化材料,金属有机膦酸化合物在过去二十多年中一直受到人们广泛的关注,并已经在离子交换、分离、催化、质子导电、光学材料等领域显示出极大的应用潜力。我们的研究目标是组装结构新颖的金属有机膦酸化合物、探索基于金属有机膦酸的新颖功能材料,目前研究重点是金属有机膦酸磁性材料、手性或极性材料以及质子导电材料, 探索性能优良的分子磁体、光学和多功能材料及与清洁能源相关的质子导电材料。

1. Molecule-based magnets (分子磁体)

The search for new low- or high-dimensional molecule-based magnets has been of intense current interest due to their potential applications in the information storage, molecular spintronics and quantum computing. Of equal importance is the modulation of magnetic behavior via external stimuli. By incorporating phosphonate ligands, we have succeeded in synthesizing a number of 3d or 4f compounds that show single molecule magnet (SMM), single-chain magnet (SCM) and long-range ordering behaviors. The tuning of the magnetic behaviors by structures and external stimulus has been investigated.

探索新的低维和高维分子磁体是当前配位化学领域的研究热点之一,在分子信息存储、分子自旋电子学和量子计算等领域具有潜在的应用。利用有机膦酸特有的配位性质,我们已经得到一系列结构新颖的过渡金属或稀土有机膦酸化合物,部分表现出单分子磁体、单链磁体和长程磁有序的性质,着重研究了结构和外界光电磁热等因素对磁性的调控作用。

The spin state of cobalt in a layered 3d-4f complex [ls-CoLa(notp)(H2O)4] •nH2O (notpH6 = 1,4,7-triazacyclononane-1,4,7-triyl-tris(methylenephosphonic acid) may be modulated in a controllable manner by the geometrical rearrangement of Co environment via the variation of the La(III) coordination sphere. (Angew. Chem. Int. Ed. 2011, 50, 5504 –5508)

By reducing the particle size to nanoscale region, compound Co3(µ3-OH)2(BTP)2 (1) (BTP = 4-(3-bromothienyl)phosphonate, Tc = 30.5 K) can vary from a soft magnet to one of the hardest molecule-based magnets at low temperature. (Chem. Eur. J. 2012, 18, 9534 – 9542)

  

The first example of iridium/lanthanide phosphonates, i.e. [DyIr6(ppy)12(bpp)2(bppH)4](CF3SO3)•8H2O (1) (ppy- = 2-phenylpyridine, bpp2- = 2-pyridylphosphonate) is reported. It shows dual functions with the photoluminescence and field-induced slow magnetization relaxation originating from the Ir and Dy moieties, respectively. (Chem. Commun. 2014, 50, 8356-8359)

A layered erbium(III) phosphonate compound, [Er(notpH4)(H2O)]ClO4•3H2O, in which the Er(III) ion has a pseudo-D5h symmetry exhibits field tunable multiple magnetic relaxation process. The near-IR emission spectrum, excited at 1064 nm (Nd:YAG laser), provides a direct probe of the crystal field splitting correlated to the magnetic data. (Chem. Commun. 2014, 50, 7621-7624)

Selected publications:

(1) S.-S. Bao, Y. Liao, Y.-H. Su, X. Liang, F.-C. Hu, Z. Sun, L.-M. Zheng,* S. Wei,* R. Alberto, Y.-Z. Li, J. Ma,* Tuning the spin state of cobalt in a Co-La heterometallic complex via controllable coordination sphere of La, Angew. Chem. Int. Ed. 2011, 50, 5504 –5508.

(2) L.-R. Guo, S.-S. Bao, B. Liu, D. Zeng, J. Zhao, J. Du, and L.-M. Zheng*, Enhanced magnetic hardness in a nanoscale metal-organic hybrid ferrimagnet, Chem. Eur. J. 2012, 18, 9534 – 9542.

(3) X.-J. Yang, M. R., S.-S. Bao, N. Hoshino, T. Akutagawa, L.-M. Zheng,* Polar metal phosphonate containing unusual 4-OH bridged double chains showing canted antiferromagnetism with large coercivity, Chem. Commun. 2014, 50, 3979-3981.

(4) D. Zeng, M. Ren, S.-S. Bao, L. Li, L.-M. Zheng,* A luminescent heptanuclear DyIr6 complex showing field-induced slow magnetization relaxation, Chem. Commun. 2014, 50, 8356-8359.

(5) M. Ren, S.-S. Bao, R. A. S. Ferreira, L.-M. Zheng,* L. D. Carlos,* A layered erbium phosphonate in pseudo-D5h symmetry exhibiting field-tunable magnetic relaxation and optical correlation, Chem. Commun. 2014, 50, 7621-7624.

(6) M. Ren, S.-S. Bao,* N. Hoshino, T. Akutagawa, B. Wang, Y.-C. Ding, S. Wei, and L.-M. Zheng*, Solvent responsive magnetic dynamics of a dinuclear dysprosium single molecule magnet, Chem. Eur. J. 2013, 19, 9619-9628.

2. Clean energy-related materials (清洁能源相关材料)

Proton-conducting materials are essential components of fuel cells and hence are very important in the field of clear energy. We aim at exploring new high-performance proton conductors based on metal phosphonates and understanding the mechanism about the proton conduction pathways.

质子导电材料是燃料电池的重要组成部分,因而在清洁能源领域具有非常重要的作用。我们的目标是探索基于金属有机膦酸的新颖高性能质子导电材料,深入研究其导电机理。

We report that a new 2D 3d-4f phosphonate [CoLa(notpH)(H2O)6]ClO4•5H2O (CoLa-II) can undergo a phase transition above 45 °C and 93% relative humidity, resulting in [H3O][CoLa(notp)(H2O)4]ClO4•3H2O (CoLa-III). The transition is accompanied with the release of the proton from intralayer to interlayer, and thus the proton conductivity of the material is increased by 1 order of magnitude. This work opens a new route in searching for high performance proton conductors. (J. Am. Chem. Soc. 2014, 136, 9292−9295.)

Selected publications:

S.-S. Bao, K. Otsubo, J. M. Taylor, Z. Jiang, L.-M. Zheng,* H. Kitagawa,* Enhancing Proton Conduction in 2D Co-La Coordination Frameworks by Solid State Phase Transition, J. Am. Chem. Soc. 2014, 136, 9292−9295.

3. Other functional metal phosphonates (其它功能材料)

Metal-organic frameworks (MOFs) are of intense current interest. Compared with the popular carboxylates, metal phosphonates possess relatively high thermal and chemical stabilities. However, phosphonate-based MOFs are still rare. On the other hand, metal phosphonates can be designed and synthesized for particular purpose simply by modifying the organic groups of the ligands. We are interested in assembling novel phosphonate-based MOFs, chiral or polar compounds in order to explore materials with multifunctions.

金属有机框架材料(MOFs)是当前的研究热点,已报道的MOFs材料大都是金属羧酸化合物。与羧酸化合物相比,金属有机膦酸化合物具有更好的热稳定性和化学稳定性,但是基于有机膦酸的MOFs材料迄今报道很少。此外,手性或极性的引入可以带来新的功能性质。我们的目标是组装新的金属有机膦酸MOFs材料、手性或极性材料,着重探索多功能金属有机膦酸材料,研究多种功能的复合与耦合。

Cobalt phosphonates Co2(pbtcH)(2,2'-bpy)2(H2O) (1) and Co2(pbtcH)(phen)2(H2O) (2) (pbtcH5 is 5-phosphonatophenyl-1,2,4-tricarboxylic acid) with layer structures can experience reversible single-crystal to single-crystal (SC–SC) structural transformations upon heating. Particularly, the breathing effect is observed for 1, accompanied with the pore-opening and closing due to the re-orientation of the coordinated 2,2'-bpy molecules. (Chem. Eur. J. 2013, 19, 16394 – 16402)

    

A chiral layered vanadium compound (VO)3(2-cpp)2(H2O)6•H2O (2-cpp3- = 2-carboxyphenylphosphonate) is obtained with enantioexcess through symmetry breaking on crystallization. Different level of enantiomeric excess is observed. (Chem. Commun. 2012, 48, 6565–6567)

A general approach to obtain pyrodiphosphonates is achieved by reacting arylphosphonic acids with AgNO3 in CH3CN under solvothermal conditions. The process is coupled with the C-C bond cleavage of acetonitrile with the formation of novel complexes [Agn(RPO2(O)O2PR)m](CN). (Chem. Commun. 2009, 2893-2895)

Selected publications:

1. Tao Zheng, Juan M. Clemente-Juan, Jing Ma, Lin Dong, Song-Song Bao, Jian Huang, Eugenio Coronado, Li-Min Zheng,* Breathing Effect in a Cobalt Phosphonate upon Dehydration/rehydration: A Single–crystal to Single–crystal Study, Chem. Eur. J. 2013, 19, 16394 – 16402.

2. J. Huang, S.-S. Bao, L.-S. Ling, H. Zhu, Y.-Z. Li, L. Pi, and L.-M. Zheng*, A racemic polar cobalt phosphonate with weak ferromagnetism, Chem. Eur. J. 2012, 18, 10839 – 10842.

3. X.-J. Yang, S.-S. Bao, T. Zheng and L.-M. Zheng*, An enantioenriched vanadium phosphonate generated via asymmetric chiral amplification of crystallization from achiral sources showing a single-crystal-to-single-crystal dehydration process, Chem. Commun. 2012, 48, 6565–6567.

4. L.-R. Guo, S.-S. Bao, Y.-Z. Li, L.-M. Zheng*, Ag(I)-mediated formation of pyrodiphosphonate coupled with C-C bond cleavage of acetonitrile, Chem. Commun. 2009, 2893-2895.