In the area of nonlinearity effects, he has focused on quasi-one-dimensional halogen-bridged metal complexes of Pt, Pd, and Ni (abbreviated as MX-Chains).  MX-Chains of Pt and Pd adopt M(II)-M(IV) mixed valence states.  On the other hand, more than 40 years ago, there were no reports on Ni MX-Chains.  He synthesized the first Ni MX-Chains, including Ni(chxn)2Br3.  Surprisingly, the Ni MX-Chains adopt Ni(III) averaged states due to strong electron-correlation (JACS, 1989), unlike Pt and Pd MX-Chains. Ni(III) MX-Chains exhibit the largest third order optical nonlinearity (Nature, 2000).  Before his research on Pd MX-Chains, there were no reports on Pd(III) averaged states.  He thought that, if the Pd-Pd distance was shortened, the Pd(III) states would be realized.  Then, by using sulfonic acids with the long alkyl-chains as counterions, he prepared the first MX-Chains with Pd(III) ions in averaged states (JACS, 2006).  This is due to the chemical pressure or fastener effects.  Moreover, by introducing triple hydrogen-bonding networks between the ligand-protons and counterions, the Pd(III) averaged state became stabilized up to 443 K, and the Pd(III) MX-Chains have the highest electrical conductivities (40 Scm-1) among the reported MX-Chains (JACS, 2017).

 

     In the case of quantum effects, Professor Yamashita synthesized several Haldane gap compounds using Ni(II) ions.  More than 40 years ago, Professor Haldane theoretically predicted that, in one-dimensional Heisenberg Antiferromagnets, there were gaps with S = integers, whereas there were no gaps with S = half integers.  The classical theory could not explain such simple phenomena.  However, Professor Haldane theoretically explained Haldane gap systems more than 40 years ago, and there were no Haldane gap compounds.  Professor Yamashita synthesized several Haldane gap compounds of [NiII(diamine)2X]Y and proved that there was a correlation between a Haldane gap (H) and exchange energies (J values) with H = 0.41 J (CCR, 2000). Professor Haldane received Nobel Prize in Physics in 2016.  Professor Glauber theoretically predicted that one-dimensional ferromagnetic Ising chain would undergo slow magnetic relaxation in 1960s. However, there were no reports on the compounds which obeyed Glauber model until Professor Yamashita along with Professor Clerac and Professor Miyasaka synthesized the first Glauber model compounds, which undergo slow magnetic relaxation.  These compounds were then named single-chain magnets (JACS, 2002).  Professor Glauber received a Nobel Prize in Physics in 2006.  Moreover, Professor Yamashita has developed single-molecule magnets (multiple-decker type phthalocyanianto Ln(III) SMMs) toward quantum molecular spintronics to overcome Moore`s limitation.  He observed “Kondo Effects” in TbPc2 SMMs on Au(111) substrates by using STM and STS for the first time (Nature Commun. 2011).  Furthermore, he was able to encapsulate SMMs into single-walled carbon nano-tubes (SWCNT), leading to the enhancement of the SMM behavior (JACS, 2018).  He has also developed single-molecule memory using TbPc2 on an Au(III) substrate by using TMR, which results in overcoming Moore`s limitation. He has also realized spin Qubits and coherence even at room temperature by using MOF (JACS, 2018).

Professor Yamashita has published more than 480 original papers, 92 review articles, and 19 books so far with 56 h-index and 14,174 citations in April in 2020.

 

     He has contributed to the organization of international and national conferences and symposiums.  When he was 42 years old, he organized Nagoya Conference titled, “Perspectives on Multifunctional Inorganic-Organic Hybrid Compounds”.  In this conference, he invited several distinguished coordination chemists from all over the world, facilitated discussions on important topics, and helped to envisage the new direction for coordination chemistry.  In 2007, he organized Asian Conference on Coordination Chemistry (ACCC) in Japan, which was followed by China(2009), India(2011), South Korea(2013), Hong Kong(2015), Australia(2017), and Malaysia(2019) and included ca. 30 countries and regions in Asia. In this century, Asia has become very important from the viewpoints of economy, resources, populations, energy, water, etc.  Now, he is an executive secretary of ACCC and one of the leaders in Asian coordination chemistry. ACCC has the following four goals: (1) to activate Asian coordination chemistry, (2) to encourage collaborations among Asian coordination chemists, (3) to encourage young and/or female coordination chemists, and (4) to activate and advance coordination chemistry in the host countries or regions. He organized the 15th International Conference on Molecule-Based Magnets (ICMM2016) in Japan in 2016.  There were more than 500 participants, which was the largest number of participants in the history ICMM.  In 2018, he organized and hosted the 43rd International Conference on Coordination Chemistry (ICCC2018) in Japan, which had the largest number of participants (> 2500).  Since 2007, he has been the chairperson for the Tohoku University Chemistry Summer School, for which graduate students and distinguished scientist from all over the world are invited to encourage the graduate students of Tohoku University to become global leaders.  When he was a chairperson of the Tohoku Branch of the Chemical Society of Japan, he organized the 70th anniversary International Conference, for which he invited two Nobel prize winners.

 

     He is a member of Activation for Chemical Society of Japan, meaning that for every annual meeting of Chemical Society of Japan, he organizes symposiums with various topics in coordination chemistry.  Moreover, in order to create the new field of Japanese coordination chemistry, he has organized a symposium titled, "Solid State Coordination Chemistry Fused with Physics and Biology", over the last ten years at Tohoku University.

 

     He has served as an Associate Editor of Bulletin of Chemical Society of Japan (CSJ), an Associate Editor of Dalton Transactions (RSC), and an Advisory Board Member of Inorganic Chemistry (ACS).  Moreover, he is a Fellow of the Royal Society of Chemistry (FRSC).

     Moreover, he is an associate member of the Science Council of Japan (SCJ), in which new directions for the sciences in Japan are discussed.

 

   For the chemistry education in Tohoku University, he has established Advanced Materials Chemistry Course (AMC course) for the foreign undergraduate students, when he was a chairman of Chemistry Department.  In this course, all classes are carried out in English.  AMC course contributes the globalization in Tohoku University.