1,722,571 research outputs found
Growth and evolution of Precambrian continental crust in the southwestern Tarim terrane: New evidence from the ca. 1.4 Ga A-type granites and Paleoproterozoic intrusive complex
No full textAbstract not availableXian-Tao Ye, Chuan-Lin Zhang, M. Santosh, Jian Zhang, Xian-Ke Fan, Ji-Jun Zhan
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Substituent Effect on Cyclopalladation of Arylimine Ligands Applied for Suzuki-Miyaura Coupling Reaction
No full text本論文主要在合成一系列不同取代之亞胺配位基，並探討其對進行環鈀化反應之影響，進而利用這些環鈀化金屬錯合物為催化劑進行耦合催化反應，並研究不同環鈀化錯合物催化之活性及可能的反應機制。
第一部份的研究中，在苯環上設計不同電子及立體效應之取代亞胺配位基，利用PdCl2(CH3CN)2與醋酸鈉於溫和的條件下進行環鈀化反應，發現此一反應的進行受到電子效應的影響不大，而是與立體效應上的取代有關，特別是當取代基為第四丁基時，反應無法進行。
經由在配基上之取代基調控，成左漲X成了系列五圓環環鈀化產物，以及在苄基位置進行碳氫活化反應形成六環的環鈀化金屬錯合物，再者這些氯橋鍵之雙核物可進行膦基取代反應，形成單一金屬中心之錯合物，此外亦製備了具有親油及親水長鏈取代的環鈀化屬錯合物。這些錯合物的分子結構皆可經由光譜以及晶體結構鑑定證明。
在Suzuki的耦合催化反應探討中，以環鈀化金屬錯合物為催化劑，對於芳香溴苯與苯基硼酸的耦合反應都有不錯的催化活性，特別是對於質子性(protic)的溶劑與在不除氧的條件下，都能顯出優秀的活性，尤其是六環的環鈀化錯合物。對於拉電子取代的芳香氯苯也有著相似的結果。特別以錯合物14j及14k對於4-甲醯基溴苯的反應為例，在濃度比為[ArBr]/ [Pd] = 106，轉換率可達90 % 以上，而4-甲氧基溴苯在相同的濃度下也可達到60 % 的轉換率，而4-甲醯基氯苯，[ArCl]/ [Pd] = 105時也有接近60% 的轉換率，若[ArCl]/ [Pd] = 104可得將近完全反應之結果。
最後在反應機制的探討上，以不同條件溫度反應時間，可得一系列不同大小之鈀金屬粒子，其中最小的約在12奈米左右，並且此一奈米鈀金屬可作為直接的佐證，做為此些催化反應中的活性物種。A series of substituted benzylidene- and dialkylarylamines reacted with PdCl2(CH3CN)2 under basic conditions at the room temperature to provide the desired cyclopalladated products (13a-i and 14j-m), even the halo substituted (Le and Lf) arylimines. The steric bulky substituent such as t-butyl on the aryl rings readily inhibits the C-H activation and only yields the simple imine-coordinated complexes (15g and 15g’, 15h). As expected, cyclometallation takes place at the ortho position of the aryl ring resulting in formation of a five-membered chelating ring. However, cyclopalladation readily occurred at benzylic to form an endo six-membered chelating ring with 14j and 14k. The resulting chloro-bridged cyclopalladated complexes underwent ligand substitution with phosphine to give the mono-nuclear palladium complexes. All complexes were characterized by both spectral and elemental analysis. Some palladium complexes were further confirmed by X-ray diffraction analysis.
Recent development on the Suzuki- Miyaura coupling reactions has been focused on the use of aryl chloride as substrates under aerobic conditions or even in aqueous solution. Accordingly, palladacycles were found to be the most promising catalysts in this regard. Thus the use of these new palladium complexes as catalysts for Suzuki-Miyaura coupling reactions was investigated in this study. It is found that this series of cyclopalladated complexes do have good catalytic activities on the Suzuki-Miyaura coupling reaction. Complexes 13a-d and 14j-m were thermally stable, not sensitive to moisture and air so that could be applied in the catalysis under aqueous and aerobic conditions. Among these catalysts, both 14j and 14k behave the best activities. Some mechanistic insights concerning this catalysis involving the palladium nano-particles were discussed.目錄
目錄 I
附圖目錄 III
附表目錄 V
附圖(Scheme)目錄 VII
論文摘要(中文) VIII
論文摘要(英文) X
第一章 緒論 1
第1-1節 環鈀化反應(Cyclopalladtion). 1
第1-2節 環鈀化金屬錯合物的應用 4
第1-3節 各類型環鈀化金屬錯合物在耦合的催化反應 5
第1-4節 反應機構之研究 14
第1-5節 研究目的 19
第二章 不同取代的亞胺配位基對於環鈀化反應的影響 20
第2-1節 配位基的合成 20
第2-2 節 環鈀化反應(Cyclopalladation). 26
第2-3 節 膦配體取代之環鈀化金屬錯合物 33
第2-4 節 結構分析 38
第2-5 節 合成含長鏈親水及親油取代之環鈀化金屬錯合物 53
第三章 環鈀化金屬錯合物在Suzuki 催化反應的應用 57
第3-1節 環鈀化錯合物對芳香溴苯的Suzuki 催化反應之研究 57
第3-2節 環鈀化錯合物對芳香氯苯的Suzuki 催化反應之研究 66
第3-3節 反應機構之研究 74
第四章 結論 82
第五章 實驗部分 85
第6-1節 測試儀器 85
第6-2節 試劑來源與前處理 86
第6-3節 實驗過程 87
第6-4節 化合物的製備 87
參考文獻 133
附錄I部分化合物之NMR光譜 141
附錄II晶體結構圖 180
附圖目錄
圖1-1 亞胺配位基進行環鈀化反應之不同的位置選擇性 3
圖1-2 環鈀化金屬錯合物對於不同配位基取代的穩定性 4
圖1-3 Beletskaya應用在Heck反應之含氮環鈀化錯合物 11
圖1-4 可能進行環鈀化反應的位置 19
圖2-1 anti-13b之氫核磁共振光譜圖 29
圖2-2 syn-13b之氫核磁共振光譜圖 29
圖2-3 環鈀化錯合物14k之氫核磁共振光譜圖 31
圖2-4 以兩當量三環己烷基膦與13a反應後之氫核磁共振光譜圖
37
圖2-5 化合物13a 之ORTEP圖 39
圖2-6化合物anti-13b 之ORTEP圖 40
圖2-7 化合物13d 之ORTEP圖 41
圖2-8化合物syn-13b 之ORTEP圖 42
圖2-9 化合物14j 之ORTEP圖 43
圖2-10 化合物14k 之ORTEP圖 44
圖2-11化合物15h 之ORTEP圖 46
圖2-12 化合物16b 之ORTEP圖 47
圖2-13 化合物19k 之ORTEP圖 48
圖2-14化合物17a之ORTEP圖 49
圖2-15 化合物20k 之ORTEP圖 50
圖2-16 化合物18a 之ORTEP圖 52
圖3-1 各種的環鈀化金屬催化劑 61
圖3-2 錯合物13a在苯基硼酸與碳酸鉀之乙醇中迴流10分鐘之TEM
77
圖3-3錯合物14j在苯基硼酸與碳酸鉀之乙醇中迴流10分鐘之TEM
78
圖3-4 錯合物14j在苯基硼酸與碳酸鉀之甲苯中迴流10分鐘之TEM
78
圖3-5 錯合物14k在苯基硼酸與碳酸鉀之乙醇中室溫反應30分鐘之TEM 79
圖3-6 錯合物20j在苯基硼酸與碳酸鉀之乙醇中迴流 5分鐘之TEM
80
圖3-7 錯合物13a在苯基硼酸與碳酸鉀之乙醇中加熱1分鐘之TEM之一80
圖3-8錯合物13a在苯基硼酸與碳酸鉀之乙醇中加熱1分鐘之TEM之二 81
附表目錄
表 1-1各類環鈀化催化劑之優缺點比較 14
表 2-1 亞胺配位基之綜合部分光譜資料表 25
表 2-2 環鈀化產物其亞胺配位基之綜合部分光譜資料表 30
表 2-3 三苯基膦配位之環鈀化產物其之綜合部分光譜資料表 35
表 2-4 含三環己烷基膦之環鈀化產物17a，20j，20k之部分光譜資料表 36
表 2-5錯合物13a, trans-13b 和13d部分鍵長(埃)鍵角(度) 40
表 2-6 錯合物cis-13b部分鍵長(埃)鍵角(度) 42
表 2-7錯合物14j部分鍵長(埃)鍵角(度) 44
表 2-8錯合物14k部分鍵長(埃)鍵角(度) 45
表 2-9 錯合物15h部分鍵長(埃)鍵角(度) 46
表 2-10 錯合物syn-13b部分鍵長(埃)鍵角(度) 47
表 2-11 錯合物19k部分鍵長(埃)鍵角(度) 48
表2-12 錯合物17a部分鍵長(埃)鍵角(度) 49
表2-13 錯合物20k部分鍵長(埃)鍵角(度) 50
表2-14 錯合物18a部分鍵長(埃)鍵角(度) 52
表2-15 含長鏈取代之亞胺配位基及其形成環鈀化產物之綜合部分光譜資料表 56
表 3-1 催化劑16b在各種溶劑下對4-甲氧基溴苯之耦合催化反應58
表 3-2 催化劑14k在各種溶劑下對4-甲氧基溴苯之耦合催化反應60
表 3-3 各種催化劑對芳香溴苯的耦合催化反應 62
表 3-4催化劑14k對4-氯乙醯苯酮與苯基硼酸的耦合反應 66
表 3-5 各種催化劑對芳香氯苯的耦合催化反應 69
表 3-6催化劑14K對各種不同的芳香基硼酸與4-甲氧基溴苯及4-乙醯基氯苯之耦合反應 73
附圖(Scheme)目錄
(Scheme 1-1) 環鈀化錯合物催化碳碳鍵或碳異核原子鍵之生成反應6
(Scheme 1-2) 鈀金屬催化Suzuki耦合反應之機制 15
(Scheme 1-3) Bedford之三級胺及三級膦之環鈀化錯合物催化機制16
(Scheme 1-4) Nolan碳烯配位之三級胺環鈀化催化劑催化機制 17
(Scheme 2-1) 一系列有取代的亞胺配位基，及其對應苯甲醛之合成21
(Scheme 2-2) 含2, 4, 6-三甲基取代的亞胺配位基Lj-Lm之合成 23
(Scheme 2-3) 環鈀化反應 27
(Scheme 2-4) 在苄基位置進行環鈀化反應 28
(Scheme 2-5) 配位基Lg及Lh未進行環鈀化反應 28
(Scheme 2-6) 合成三苯基膦配位之環鈀化錯合物 34
(Scheme 2-7) 合成三環己烷基膦配位之環鈀化錯合物 36
(Scheme 2-8) 合成兩當量三環己烷基膦配位之環鈀化錯合物 37
(Scheme 2-9) 合成含長鏈親水及親油取代之環鈀化金屬錯合物 54
(Scheme 3-1) 可能的產生活性催化物種之途徑 7
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